Fix input width in MultiSelect UI components - replacement solution

[mikiher]

This a a replacement of #2701 (which doesn't fully work), and now it really fixes #2700.

In this solution:

• We remove the style property from the input element in the template altogether, replacing it with a w-6 tailwind class (which translates to width: 24px).
• This change (for some reason not obvious to me) enables setInputWidth to work again, so we bring it back.
• Now we just need to reset the width back to 24px after we're done editting.

I chose to use 24px instead of the original 40px because this is the calculated width of an empty input in setInputWidth

This now works well, fixes the issues that #2701 had.

[advplyr]

This is working for all my tests, thanks!