Fix the hanging problem of region spectral profiles when a region is deleted

[markccchiang]

Description

• What is implemented or fixed? Mention the linked issue(s), if any. Closes #1328.

• How does this PR solve the issue? Give a brief summary. This problem is due to the deadlock of two mutexes, _active_task_mutex and _region_mutex, in the RegionHandler methods. When a region spectral profile process starts, _active_task_mutex is taken in the method GetRegionSpectralData. Then the _region_mutex will be frequently taken inside this method RegionFileIdsValid to check whether the region object exists or it is disconnected. If we delete the region during this process, the RemoveRegion method is called, and the _region_mutex is taken here inside this function. Then it waits to take _active_task_mutex in the WaitForTaskCancellation. Two methods GetRegionSpectralData and RemoveRegion are waiting for the same mutexes _active_task_mutex and _region_mutex. The solution is to remove the _region_mutex from the RegionSet method. Since it only reads the status of region objects and does not modify the _regions map. Removing this mutex allows the RegionFileIdsValid to get rid of _region_mutex (since it can be taken by RemoveRegion at the same time), so it can pass the disconnected signal and stop the region spectral profile process. Finally, the region object can be deleted.

• Are there any companion PRs (frontend, protobuf)? No.

• Is there anything else that testers should know (e.g. exactly how to reproduce the issue)? The hanging problem of region spectral profiles should be solved.

Checklist

• [x] changelog updated ~/ no changelog update needed~
• [x] e2e test passing / corresponding fix added / new e2e test created
• [x] ~protobuf updated to the latest dev commit /~ no protobuf update needed
• [x] ~protobuf version bumped /~ protobuf version not bumped
• [ ] added reviewers and assignee
• [ ] added ZenHub estimate, milestone, and release

[github-actions[bot]]

Package	Line Rate	Health
src.Cache	68%	➖
src.DataStream	52%	➖
src.FileList	67%	➖
src.Frame	50%	➖
src.HttpServer	42%	➖
src.ImageData	28%	❌
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src.ImageStats	76%	✔
src.Logger	38%	➖
src.Main	52%	➖
src.Region	18%	❌
src.Session	29%	❌
src.Table	52%	➖
src.ThreadingManager	87%	✔
src.Timer	85%	✔
src.Util	48%	➖
Summary	38% (7091 / 18732)	❌