[3.x] Update vueselect dependency to v3

[mazeeblanke]

Update vue select to version 3.

1. Replaced the onSearch prop with the search event has using the same parameters in it's place.
2. import the css file for the vue-select

[tchapi]

That would close #626 I think, that would be really nice !

[ifox]

Thanks @mazeeblanke! I tested this and it looked like we are losing our CSS customization on select fields powered by vue-select.

[mazeeblanke]

@ifox thank you for the feedback. I will go through it again and fix it

[haringsrob]

I think that since we are on this we can also add support for the selectable https://vue-select.org/guide/selectable.html#selectable-prop option.

We could take a similar array as the options.

[haringsrob]

Moving this onto 3.x

[codecov]

Codecov Report

Merging #674 (02c1660) into 3.x (8c3dc56) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                3.x     #674   +/-   ##
=========================================
  Coverage     58.59%   58.59%           
  Complexity     2779     2779           
=========================================
  Files           176      176           
  Lines          8432     8432           
=========================================
  Hits           4941     4941           
  Misses         3491     3491           

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