github swallows errors even if fetching issues fails

[seanstory]

part of #2393

Description

The github connector is currently just logging a warning instead of propagating an error, if something goes wrong while fetching issues. See:

connectors/connectors/sources/github.py

Lines 1373 to 1377 in 8c8d4a3

	except Exception as exception:
	self._logger.warning(
	f"Something went wrong while fetching the repository. Exception: {exception}",
	exc_info=True,
	)

This error should probably be re-raised if it's not something that can be re-tried. If the github connector cannot sync any issues at all, the sync should fail. If it's just a single issue or two, that's probably ok for a WARN message.

Acceptance Criteria

• github connector fails syncs if no issues can be synced
• github connector attempts retries for errors that look transient
• errors with limited scope (single documents, or edge cases) can be moved past with sufficient WARN logging

[artem-shelkovnikov]

I did some digging into the code and wanted to raise the following additional issues that need to be addressed:

1. There should be no except Exception in code. Exceptions should be properly handled - for example the git library we use has https://gidgethub.readthedocs.io/en/latest/__init__.html#gidgethub.GitHubException as base exception class - we need to switch to catching this class.
2. This code should not raise exception, instead caller of this code must re-raise the RateLimitingError
3. This code should re-raise
4. This code should re-raise
5. This code should re-raise
6. This code should re-raise
7. This code should re-raise

[artem-shelkovnikov]

@praveen-elastic this ticket was mistakenly marked as "enhancement" - it's a critical bug, can we prioritise fixing it?

[khushbu-elastic]

@DianaJourdan As we discussed in the meeting, please take a note.

NOTE: We are blocked for this issue as we are waiting for approach finalization in the similar issue - #2394
Once the finalized approach is completely implemented in that issue will prioritize this issue and work on it.