chore: Run MMI tests on long-running branches (#28651)

## **Description**

The `check_mmi_trigger.sh` script has been updated to run MMI-related
tests on long-running branches (`develop`, `master`, and RCs). This is
intended to make it easier for us to detect these regressions sooner, so
that we don't waste time tracking down the commit that caused any given
breakage.
[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/28651?quickstart=1)

## **Related issues**

No linked issue. This is intended to make it safer to extend the use of
this MMI filter to other jobs, which will help us save CircleCI credits

## **Manual testing steps**

I tested this locally by running the script with the
`CIRCLE_PULL_REQUEST`, `GITHUB_TOKEN`, and `CIRCLE_BRANCH` environment
variables set. e.g.

```
> CIRCLE_PULL_REQUEST=foo GITHUB_TOKEN=foo CIRCLE_BRANCH=Version-v12.0.0 ./.circleci/scripts/check_mmi_trigger.sh
Long-running branch detected, running MMI tests.
```

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

.circleci/scripts/check_mmi_trigger.sh

@@ -9,6 +9,12 @@ if [ -z "$CIRCLE_PULL_REQUEST" ] || [ -z "$GITHUB_TOKEN" ]; then
   exit 0
 fi
 
+if [[ $CIRCLE_BRANCH = 'develop' || $CIRCLE_BRANCH = 'master' || $CIRCLE_BRANCH =~ ^Version-v[0-9.]* ]]; then
+  echo "Long-running branch detected, running MMI tests."
+  echo "run_mmi_tests=true" > mmi_trigger.env
+  exit 0
+fi
+
 # Extract PR number from the pull request URL
 PR_NUMBER=$(echo "$CIRCLE_PULL_REQUEST" | awk -F'/' '{print $NF}')