Resolve bug with searching databases and impact categories

[marc-vdm]

• resolve #1031 .
• Implement stripping of whitespace on all search fields (databases and impact categories tables)
• Implement autosearch after 300ms of no input on all search fields
• remove some unused code from impact categories widget...

Checklist

• [x] Keep pull requests small so they can be easily reviewed.
• [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] Request a review from another developer.

[coveralls]

coverage: 50.641% (+0.3%) from 50.33% when pulling 1ffe7a1900157677f177808474a068a42c565486 on marc-vdm:search_bug into 51566ac32c80bbc40d4f976084dbb1a8ee88f985 on LCA-ActivityBrowser:master.

[github-actions[bot]]

This issue has been implemented in the new release of Activity Browser 🚀 (version 2.9.3), you can get the new version by updating Activity Browser.

🤖beep boop! I'm a bot and this message was an automated action. If updating does not make sense for this issue, just ignore this.