fix bug with LabeledSelect with "multiple" attribute

[aalves08]

Summary

Fixes #12117

Occurred changes and/or fixed issues

• fix issue with LabeledSelect in mode multiple by allowing the binding of the attribute to the element v-select that was incorrectly being filtered out

Technical notes summary

Areas or cases that should be tested

• Test repro case(s) in issue + test some other areas that use LabeledSelect with multiple="true"

Areas which could experience regressions

• Just to discard any regressions, do a quick test of different instances of LabeledSelect, even if they don't use multiple="true"

Screenshot/Video

Checklist

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[cnotv]

I am not so sure this is the whole issue here. When I searched for other cases, I could not reproduce them equally. Investigating the issue specifically, resulted in trying to map a string of the term:

In your PR this issue is fixed, although I suspect there's something further around the attributes clashing here.

For the sake of solving the issue, we can ignore the attribute inheritance confusion, although we should bare mind.

[cnotv]

I've added a unit test that seems to validate the behavior change from string to array in case of multiple.
The other case has a different event handler which is not a bidirectional binding.

[cnotv]

LGTM

Storybook seems not achievable atm