Support for TRY-FINALLY structure in procedural SQL

[EPluribusUnum]

Hi *!

When you want to cleanup after transaction independent writes (rdb$set_context, autonomous transaction, execute statement on external, UDR, etc..), now you have to implement the cleanup in the happy path and in exception path also. It would be great to have try-finally structure support for cleanup, so you have to implement cleanup only in one place.

Thank you!