Make metrics dashboard embeds work with new and old URLs

What does this MR do?

We added a new dashboard route in #226002. The goal was to have a dashboard route that does not contain an environment ID, so that we can move towards a metrics dashboard that does not require an environment to exist.

Dashboard embeds should work with these new routes as well as the old. This MR updates the regex used by the GFM to recognize metrics dashboard URLs so that it matches the new URL as well.

Old URL: https://<host>/<namespace>/<project>/-/environments/<env_id>/metrics

New URL: https://<host>/<namespace>/<project>/-/metrics?environment=<env_id>

Issue: #227929 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
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