Implement multi select from gitlab-ui in issue lists

Remaining work for %16.8

label filter needs to be updated and group_multi_select_tokens feature flag needs to be defaulted to on.

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In gitlab-ui#2162 (closed), we are updating gl-filtered-search to use multi select. Once that is complete, we will want to update the issue list in the GitLab product to use if for OR filtering.

Availability and Testing

Regression testing, please make sure e2e:package-and-test job is passing.

Ensure updated test coverage in unit/integration/feature tests.