feat(launcher): add test database initialization helping macros

[rimrakhimov]

Helps when initializing database inside tests. Allows not to provide the test case name as it automatically uses the place that function is defined instead.

Note!!: using it with rstest parameterized test cases (https://docs.rs/rstest/latest/rstest/attr.rstest.html#test-parametrized-cases) results in the same database name for all cases. In such cases, you have to manually provide some meaningful suffix as a database! or database_name! argument (the second macros branches)

Can be used inside test in the following way (the migration crate has a name migration_crate):

use blockscout_service_launcher::test_database::database;
...
#[tokio::test]
async fn test() {
    let db_guard = database!(migration_crate);
    ...
}

[bragov4ik]

Let's add the note and usage example to the macro documentation?