Change all label tooltips to interactive popovers

Issue Moved To https://gitlab.com/gitlab-org/gitlab-ee/issues/27324

internal customer since GitLabbers use labels heavily.

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Problem to solve

We currently have links included in label tooltips, which are not particularly helpful as tooltips disappear as soon as you hover outside the element.

Proposal

From @cperessini's comment in gitlab-design#282 (comment 150466105)