[2.x] Closes monolog handlers by event listener if the worker stops

[NiroDeveloper]

Fix for #850
Laravel uses Monolog for logging, some monolog handler have a important close() function.
Octane does never call this function! In normal laravel applications, monolog calls close by itself via __destruct().
It seams like __destruct() is never called in Swoole, so close the handler manually per event.

[taylorotwell]

Drafting until @nunomaduro can review.

[taylorotwell]

@NiroDeveloper how did you decide it should be placed on WorkerStopping? Why not OperationTerminated?

[NiroDeveloper]

The handler should be reused for every request / operation, so it should just call close() at the end of the worker process.
There is already a FlushMonologState listener that calls reset() on the handler between every request, this is the correct behavior as descripted by monolog.

[taylorotwell]

Thanks @NiroDeveloper