Add timeout on thread join on shutdown and suppress ThreadAbortException

[rblenkinsopp]

Summary

The timeout on the thread join matches the maximum amount of time that should be spent on a PollConnection anyway, before the thread is aborted. ThreadAbortExceptions are now explicity caught and suppressed without logging to avoid erroneous log messages in normal operation.

Contributor Tasks

• Add a CHANGELOG entry for this change.
• Ensure documentation requirements are met e.g., public API is commented.
• Consider any licensing/other legal implications for this MR e.g. notices required by any new libraries.

Reviewer Tasks

• Code reviewed.
• Non-code assets e.g. Unity assets/scenes reviewed.
• All tests must be ran and cover all scenarios (If not, add new tests to the cycle and run them).
• Documentation has been reviewed.
• Approve with a comment of any additional tests run or any observations.

Related Issues

This should hopefully resolve #1708