create ci dispatch flow

[ben-c-at-moz]

Relevant Links

Bugzilla: Bug

Description of Code / Doc Changes

• Creates script to check whether l10n tests, smoke tests, or both should be run on a given pull request (choose_test_channel.py)
• Creates new GHA flow to execute that script and use the results to select the correct test sets to run
• Update TC to account for smoke Linux
• Update the other GHA flows so that they no longer run on PRs (are only kicked off by the dispatcher), other changes to make sure they still work
• lint
• (I have tested on smoke and smoke+l10n, we need to test against scheduled beta soon after merge)

Process Changes Required

Mark the relevant boxes:

• Changes CI flow
• Changes scheduled Beta or DevEdition
• Changes Git hooks or Github settings

Screenshots or Explanations

Note that now the dispatcher GHA flow is the only GHA kicked off by pull requests. It then kicks off the smoke and/or l10n flows, much the same way scheduled beta / devedition Cron does.

Comments or Future Work

It would probably be good to streamline the L10n mapping selections further.

Workflow Checklist

• Please request reviewers
• If this is an unblocker, please post in Slack.
• If asked to address comments, please resolve conversations.
• If asked to change code, please re-request review from the person who wanted changes.

Thank you!

[philimon-reset]

Awesome script.