libsql: Deasyncify some Conn trait methods

[penberg]

There's no reason to have is_autocommit(), changes() or last_insert_row() methods async because they're all fully local and cannot block. Deasyncify them.

[haaawk]

LGTM but CI says you missed some places:

error[E0277]: `i64` is not a future
   --> libsql-server/tests/hrana/batch.rs:137:45
    |
137 |         assert_eq!(conn.last_insert_rowid().await, 1, "1st row id");
    |                                            -^^^^^
    |                                            ||
    |                                            |`i64` is not a future
    |                                            help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `i64`
    = note: i64 must be a future or must implement `IntoFuture` to be awaited
    = note: required for `i64` to implement `std::future::IntoFuture`

error[E0[27](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:28)7]: `i64` is not a future
   --> libsql-server/tests/hrana/batch.rs:143:45
    |
143 |         assert_eq!(conn.last_insert_rowid().await, 3, "3rd row id");
    |                                            -^^^^^
    |                                            ||
    |                                            |`i64` is not a future
    |                                            help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `i64`
    = note: i64 must be a future or must implement `IntoFuture` to be awaited
    = note: required for `i64` to implement `std::future::IntoFuture`

error[E0277]: `i64` is not a future
   --> libsql-server/tests/hrana/batch.rs:147:45
    |
147 |         assert_eq!(conn.last_insert_rowid().await, 3, "last row id unchanged");
    |                                            -^^^^^
    |                                            ||
    |                                            |`i64` is not a future
    |                                            help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `i64`
    = note: i64 must be a future or must implement `IntoFuture` to be awaited
    = note: required for `i64` to implement `std::future::IntoFuture`

error[E0277]: `bool` is not a future
   --> libsql-server/tests/standalone/mod.rs:[33](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:34)9:38
    |
339 |         assert!(conn.is_autocommit().await);
    |                                     -^^^^^
    |                                     ||
    |                                     |`bool` is not a future
    |                                     help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `bool`
    = note: bool must be a future or must implement `IntoFuture` to be awaited
    = note: required for `bool` to implement `std::future::IntoFuture`

error[E0277]: `bool` is not a future
   --> libsql-server/tests/standalone/mod.rs:[34](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:35)3:39
    |
343 |         assert!(!conn.is_autocommit().await);
    |                                      -^^^^^
    |                                      ||
    |                                      |`bool` is not a future
    |                                      help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `bool`
    = note: bool must be a future or must implement `IntoFuture` to be awaited
    = note: required for `bool` to implement `std::future::IntoFuture`

error[E0277]: `bool` is not a future
   --> libsql-server/tests/standalone/mod.rs:346:38
    |
346 |         assert!(conn.is_autocommit().await);
    |                                     -^^^^^
    |                                     ||
    |                                     |`bool` is not a future
    |                                     help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `bool`
    = note: bool must be a future or must implement `IntoFuture` to be awaited
    = note: required for `bool` to implement `std::future::IntoFuture`

error[E0277]: `bool` is not a future
   --> libsql-server/tests/standalone/mod.rs:[35](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:36)1:41
    |
351 |             assert!(!tx.is_autocommit().await);
    |                                        -^^^^^
    |                                        ||
    |                                        |`bool` is not a future
    |                                        help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `bool`
    = note: bool must be a future or must implement `IntoFuture` to be awaited
    = note: required for `bool` to implement `std::future::IntoFuture`

error[E0277]: `bool` is not a future
   --> libsql-server/tests/standalone/mod.rs:352:42
    |
352 |             assert!(conn.is_autocommit().await); // connection is still autocommit
    |                                         -^^^^^
    |                                         ||
    |                                         |`bool` is not a future
    |                                         help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `bool`
    = note: bool must be a future or must implement `IntoFuture` to be awaited
    = note: required for `bool` to implement `std::future::IntoFuture`

error[E0277]: `bool` is not a future
   --> libsql-server/tests/standalone/mod.rs:358:[38](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:39)
    |
358 |         assert!(conn.is_autocommit().await);
    |                                     -^^^^^
    |                                     ||
    |                                     |`bool` is not a future
    |                                     help: remove the `.await`
    |
    = help: the trait `futures_core::Future` is not implemented for `bool`
    = note: bool must be a future or must implement `IntoFuture` to be awaited
    = note: required for `bool` to implement `std::future::IntoFuture`

For more information about this error, try `rustc --explain E02[77](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:78)`.
error: could not compile `libsql-server` (test "tests") due to 9 previous errors
Error: The process '/home/runner/.cargo/bin/cargo' failed with exit code [101](https://github.com/tursodatabase/libsql/actions/runs/8155781344/job/22292009232?pr=1135#step:6:102)