Show label names in collapsed issuable sidebar label tooltip

Right now, the labels can only be found by expanding the issuable sidebar, which is annoying.

/cc @jschatz1

Let's just add a tool tip. Should take a few seconds. cc @iamphill

Milestone changed to %8.11

Milestone changed to %8.10

Reassigned to @iamphill

mentioned in merge request !5232 (merged)

mentioned in commit c0cc6766

Milestone changed to %8.11

mentioned in commit c7ad5e7b

mentioned in commit 8f06cfca

mentioned in commit 2143e2bb

mentioned in commit 40cd1b3e

mentioned in commit 931274ba

Status changed to closed by merge request !5232 (merged)

mentioned in commit 930b1e4e

Mentioned in commit 931274ba

Mentioned in commit 4ecfd74f

mentioned in merge request !14785