fix(pgdialect): Remove unsigned integer conversion

[Aoang]

PostgreSQL does not support unsigned integer types. Previously, a Go uint32 type was mapped to the database integer type. When values exceeded the range, they were converted.
Even specifying the type as numeric did not prevent this conversion. This update removes the conversion, allowing the database to handle errors appropriately.

Fixed #624

[j2gg0s]

I’d like to elaborate on the specific impacts.

Assume we use uint32 in a struct in Go, Bun will create table with Integer in Postgres.

type User struct {
        ID     int `bun:",pk"`
        Name   string
        Uint32 uint32
        Int64  int64
}

bun=# \d users;
                    Table "public.users"
 Column |       Type        | Collation | Nullable | Default
--------+-------------------+-----------+----------+---------
 id     | bigint            |           | not null |
 name   | character varying |           |          |
 uint32 | integer           |           |          |
 int64  | bigint            |           |          |
Indexes:
    "users_pkey" PRIMARY KEY, btree (id)

If we insert 1<<31+1, we got -2147483647.
But we can got it by 1<<31+1.

	users := []*User{
		{ID: 1, Name: "user 1", Uint32: 1<<31 - 1},
		{ID: 2, Name: "user 2", Uint32: 1<<31 + 1},
	}
	if _, err := db.NewInsert().Model(&users).Exec(ctx); err != nil {
		panic(err)
	}

	{
		user := User{}
		if err := db.NewSelect().Model(&user).Where("uint32 = ?", uint32(1<<31+1)).Scan(ctx); err != nil {
			panic(err)
		}
		fmt.Println(user)
	}

[bun]  13:57:53.983   INSERT                  742µs  INSERT INTO "users" ("id", "name", "uint32", "int64") VALUES (1, 'user 1', 2147483647, 0), (2, 'user 2', -2147483647, 0)
[bun]  13:57:53.983   SELECT                  314µs  SELECT "user"."id", "user"."name", "user"."uint32", "user"."int64" FROM "users" AS "user" WHERE (uint32 = -2147483647)

With this PR, we will got error when insert:

[bun]  13:58:43.396   INSERT                1.541ms  INSERT INTO "users" ("id", "name", "uint32", "int64") VALUES (1, 'user 1', 2147483647, 0), (2, 'user 2', 2147483649, 0)    pgdriver.Error: ERROR: integer out of range (SQLSTATE=22003)

Although this may break some edge cases of runnable code, I still believe this is a good change.