Always close thread-specific SQLite connections

[mrvisscher]

Fixes an issue where thread-specific SQLite database connections persisted even after said thread was finished, resulting in undeletable projects and segmentation faults. Now, by using run_safely() instead of run() within a reimplemented ABThread, all connections are closed after a thread finishes work.

Probably interesting to you @haasad , as this relates to #1124 and enables us to use Python 3.10 as well.

• [x] Update the CopyDatabaseThread as well

• closes #1078

Checklist

• [x] Keep pull requests small so they can be easily reviewed.
• [x] Update the documentation, please follow the numpy style guide.
• [ ] Update tests.
• [x] Categorize the PR by setting a good title and adding one of the labels: bug, feature, ui, change, documentation, breaking, ci as they show up in the changelog.
• [x] Link this PR to related issues by using closing keywords.
• [x] Add a milestone to the PR for the intended release.
• [x] Request a review from another developer.

[coveralls]

coverage: 50.857% (-0.001%) from 50.858% when pulling 026ad4bbc050cf3869daf631b6e52c8236e24fdb on mrvisscher:thread-database-closer into ebbc322da7beebacc5b198448c9ce2260a191972 on LCA-ActivityBrowser:master.

[mrvisscher]

Thanks for your comments and review @haasad, happy you're happy! 😄