[VSA] License check for Lead Time For Changes (DORA)

Problem to solve

We plan to display the DORA Lead Time For Changes metric in VSA. Before that, we must ensure the data is subject to the correct license check.

Proposal

Add a license check in VSA that will allow DORA Lead Time For Changes to be displayed for GitLab Ultimate, but not for GitLab Premium or GitLab Free. In other words, only expose the DORA metric if the license check is successful. (This is very similar to the license check for DORA Deployment Frequency.)