Make Multiselect conditionally rendered

[ElectronicBlueberry]

Second fix for #17250

Causes the vue multiselect component used inside the stateless tags component to unmount when closed, and uses custom elements to render the closed state instead.

How to test the changes?

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• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

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[ElectronicBlueberry]

superseded by #17331