CLD-7553 Implement per-MM_ENV runs, post the E2E test links back to user

[mvitale1989]

Summary

Support running multiple E2E Tests per-PR, one per MM_ENV specification.
Also post back the Workflow and Automation Dashboard URLs as soon as possible in the run.

Tested by running with the following settings:

• Leaving MM_ENV empty
• Setting MM_ENV to MM_SUPPORTSETTINGS_HELPLINK=https://about.mattermost.com/default-help/?dummy

Note that in the future, the E2E Tests/test status check (created by runs that leave MM_ENV empty) will be the only one required for PR mergeability.

Ticket Link

https://mattermost.atlassian.net/browse/CLD-7553
https://mattermost.atlassian.net/browse/CLD-7647

Release Note

NONE

[github-actions]

E2E test run is starting for commit a4d9e1ab9ab0bea76a0ccd1a93d2444472a286a5.
You can check its progress by either:

• Looking at the corresponding commit status, which will be available in a few moments: E2E Tests/test.
• Looking at the E2E test's Workflow Run, with Run ID 9130673929.
• Looking at the E2E test's Cycle on the Automation Dashboard.

[github-actions]

E2E test run is starting for commit a4d9e1ab9ab0bea76a0ccd1a93d2444472a286a5, with MM_ENV=MM_SUPPORTSETTINGS_HELPLINK=https://about.mattermost.com/default-help/?dummy.
You can check its progress by either:

• Looking at the corresponding commit status, which will be available in a few moments: E2E Tests/test/e2ca64c1.
• Looking at the E2E test's Workflow Run, with Run ID 9130705449.
• Looking at the E2E test's Cycle on the Automation Dashboard.

[github-actions]

E2E test run is starting for commit a4d9e1ab9ab0bea76a0ccd1a93d2444472a286a5, with MM_ENV=MM_SUPPORTSETTINGS_HELPLINK=https://about.mattermost.com/default-help/?dummy.
You can check its progress by either:

• Looking at the corresponding commit status, which will be available in a few moments: E2E Tests/test/e2ca64c1.
• Looking at the E2E test's Workflow Run, with Run ID 9130727290.
• Looking at the E2E test's Cycle on the Automation Dashboard.

[mvitale1989]

The test was performed as follows (E2E tests were started manually from the Actions tab):

1. A job with an empty MM_ENV was started, which replied with the first comment
2. A new job was started with MM_ENV equal to MM_SUPPORTSETTINGS_HELPLINK=https://about.mattermost.com/default-help/?dummy, which replied with the second comment
3. A third job was started with the same MM_ENV as the second job. This resulted in the second job being automatically canceled because of the concurrency directive.

Concurrency works as expected, so you can run multiple E2E tests with different MM_ENV values in the same PR.

Also note that the last two jobs were canceled before they could generate the test cycle on the automation dashboard.

[saturninoabril]

So nice! Thanks @mvitale1989!