Gracefully Handle HTCondor Collector Updates

[giffels]

• Extend AsyncCacheMap to grant r/o access to cached data
• Implement function to HTCondor Collector machines
• Implement function to get DaemonStartTime of HTCondor Master daemon
• Take into account DaemonStartTime when updating machine status
• Add new mocked executor utility to support multiple consectuive responses to executor.run_command calls
• Add tests for new features

Fixes #376

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.05%. Comparing base (58b66e0) to head (973f49a).
⚠️ Report is 58 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #378      +/-   ##
==========================================
+ Coverage   98.94%   99.05%   +0.11%     
==========================================
  Files          55       55              
  Lines        2266     2338      +72     
==========================================
+ Hits         2242     2316      +74     
+ Misses         24       22       -2     

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[giffels]

For the time being, the new mocked executor utility is called mock_executor_run_command_new. I will open a new issue to refactor other adapters that currently use mock_executor_run_command. Once that is done, mock_executor_run_command_new will replace the old mock_executor_run_command as the standard utility.

[giffels]

Not really part of the feature, but fixing Type Hints is always good when visting the code anyhow.

[giffels]

Stil in draft mode, but reviewers are already invited to comment about the implementation. :-)

[maxfischer2781]

This is extremely specific now. I guess you can just check for identity as return self is other (which then also doesn't need the type check).

[giffels]

I changed that as well. Thanks for spotting this.

[maxfischer2781]

Looks good to me. I've got a general maintenance comment, but it doesn't have to be forced into this PR.

[maxfischer2781]

Just realised I let this sit for a while. Thanks for the updates, LGTM.