fix(database, web): Stop transaction & stream handling exceptions from throwing twice

[russellwheatley]

Description

1. Removed transaction handler from throwing twice. This is the main fix in the PR because we were using two exception handlers so when the second exception was passed into convertFirebaseDatabaseException(), it would pass in an already formed FirebaseException and cause the users issue.
2. Moved exception stream handling to the source so we can properly propagate exception without unhandled exception. We already have test catching exception, the problem here was an unhandled exception was also thown.
3. Implemented the same logic for stream exception handling for once() API function.
4. Wrote test for transaction exception handling.

Related Issues

closes https://github.com/firebase/flutterfire/issues/12675

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Breaking Change

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