Restore value watcher to update selection

[rtibbles]

Description

• Restores a watcher that helps keep the internal selection state of KSelect in line with the value prop

Changelog

• Description: Restore value watcher to update selection in KSelect
• Products impact: bugfix
• Addresses: Search - 'Clear all' is not resetting the dropdowns kolibri#12821
• Components: KSelect
• Breaking: no
• Impacts a11y: no
• Guidance: Fixes a regression

Steps to test

1. Step 1
2. Step 2
3. ...

(optional) Implementation notes

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical and brittle code paths are covered by unit tests
• The change is described in the changelog section above

Reviewer guidance

• Is the code clean and well-commented?
• Are there tests for this change?
• Are all UI components LTR and RTL compliant (if applicable)?
• Add other things to check for here

Comments

[AlexVelezLl]

Code changes makes sense, and just tested it on Kolibri, and can confirm that this fixes learningequality/kolibri#12821.