… once per batch (#1482) (#1483)

This is a backport of #1482 to `4.1.x`

JAVA-5572

- Resolve an issue where exceptions thrown during thenRun, thenSupply, and related operations in the asynchronous API were not properly propagated to the completion callback. This issue was addressed by replacing `unsafeFinish` with `finish`, ensuring that exceptions are caught and correctly passed to the completion callback when executed on different threads.

- Update existing Async API tests to ensure they simulate separate async thread execution.

- Modify the async callback to catch and handle exceptions locally. Exceptions are now directly processed and passed as an error argument to the callback function, avoiding propagation to the parent callback.

- Move `callback.onResult` outside the catch block to ensure it's not invoked twice when an exception occurs.

JAVA-5562

Ensures that the deferredElement name is reset correctly.
Test case ported to bson-kotlin

JAVA-5524

bson-kotlin optional type fix
Port bson-kotlin test to bson-kotlinx (#1452)

JAVA-5365