feat: deprioritize E2E jobs on Cirrus runners (#29837)

## **Description**

When Cirrus runner capacity is saturated, release/production build jobs
compete equally with E2E builds, test runs, and fixture updates for
runner slots. This means a time-sensitive release build can be queued
behind dozens of E2E jobs triggered by PR pushes.

Cirrus Runners supports a binary priority system (regular and
`low-priority`). This PR adds `low-priority` to all E2E/non-release
Cirrus runner jobs so release pipeline jobs are serviced first during
capacity saturation. When capacity is available, all jobs start
immediately with no change in behavior.

**Jobs deprioritized (E2E, non-release):**
- `build-android-e2e.yml` - E2E Android APK build
- `build-ios-e2e.yml` - E2E iOS app build
- `run-e2e-workflow.yml` - E2E test execution (both platforms)
- `update-e2e-fixtures.yml` - Fixture export/update

**Jobs kept at regular priority (release pipeline):**
- `build.yml` - Production/release native build
- `setup-node-modules.yml` - Dependency setup for production builds
- `upload-to-testflight.yml` - TestFlight upload

The `actionlint.yaml` config already includes `low-priority` as a known
self-hosted runner label (line 17).

**Note:** A similar but narrower change was attempted in #19091 (Sep
2025, iOS E2E only, 1 file) and reverted in #19379 (12 days later, no
documented reason). This PR covers both platforms and all 4 E2E workflow
files.

Part of MCWP-574 (PR 5 of 5).

## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes: MCWP-574

## **Manual testing steps**

```gherkin
Feature: Cirrus runner job priority for release pipeline

  Scenario: E2E jobs run normally when capacity is available
    Given Cirrus runner capacity is not saturated
    When an E2E workflow is triggered (build or test)
    Then the job starts immediately with no delay
    And the job completes successfully

  Scenario: Release jobs are prioritized during capacity saturation
    Given Cirrus runner capacity is near saturation with E2E jobs
    When a release/production build is triggered via build.yml
    Then the release build job is allocated a runner before queued E2E jobs
    And E2E jobs resume after runners free up
```

## **Screenshots/Recordings**

N/A - CI pipeline change, no UI impact.

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.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
- [ ] 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-mobile/blob/main/.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.

Author: Qbandev

.github/workflows/build-android-e2e.yml

@@ -34,7 +34,7 @@ on:
 jobs:
   build-android-apks:
     name: Build Android E2E APKs
-    runs-on: ${{ inputs.runner_provider == 'namespace' && 'namespace-profile-metamask-android-build' || 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-lg' }} # Optimized for lg runner (48GB) with conservative memory settings
+    runs-on: ${{ inputs.runner_provider == 'namespace' && 'namespace-profile-metamask-android-build' || (startsWith(github.base_ref, 'release/') && fromJSON('["ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-lg"]') || fromJSON('["ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-lg", "low-priority"]')) }} # Optimized for lg runner (48GB) with conservative memory settings
     timeout-minutes: 40
     env:
       GRADLE_USER_HOME: ${{ inputs.runner_provider == 'namespace' && '/home/runner/_work/.gradle' || '/home/admin/_work/.gradle' }}

.github/workflows/build-ios-e2e.yml

@@ -30,7 +30,7 @@ permissions:
 jobs:
   build-ios-apps:
     name: Build iOS E2E Apps
-    runs-on: ${{ inputs.runner_provider == 'namespace' && 'namespace-profile-metamask-ios-build' || 'ghcr.io/cirruslabs/macos-runner:tahoe-xl' }}
+    runs-on: ${{ inputs.runner_provider == 'namespace' && 'namespace-profile-metamask-ios-build' || (startsWith(github.base_ref, 'release/') && fromJSON('["ghcr.io/cirruslabs/macos-runner:tahoe-xl"]') || fromJSON('["ghcr.io/cirruslabs/macos-runner:tahoe-xl", "low-priority"]')) }}
     outputs:
       artifacts-url: ${{ steps.set-artifacts-url.outputs.artifacts-url }}
       app-uploaded: ${{ steps.upload-app.outcome == 'success' }}

.github/workflows/run-e2e-workflow.yml

@@ -63,7 +63,7 @@ on:
 jobs:
   test-e2e-mobile:
     name: ${{ inputs.test-suite-name }}
-    runs-on: ${{ inputs.runner_provider == 'namespace' && (inputs.platform == 'ios' && 'namespace-profile-metamask-ios-e2e' || 'namespace-profile-metamask-android-build') || (inputs.platform == 'ios' && 'ghcr.io/cirruslabs/macos-runner:tahoe' || 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-lg') }}
+    runs-on: ${{ inputs.runner_provider == 'namespace' && (inputs.platform == 'ios' && 'namespace-profile-metamask-ios-e2e' || 'namespace-profile-metamask-android-build') || (startsWith(github.base_ref, 'release/') && fromJSON(format('["{0}"]', inputs.platform == 'ios' && 'ghcr.io/cirruslabs/macos-runner:tahoe' || 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-lg')) || fromJSON(format('["{0}", "low-priority"]', inputs.platform == 'ios' && 'ghcr.io/cirruslabs/macos-runner:tahoe' || 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-lg'))) }}
     outputs:
       apk-target-path: ${{ steps.determine-target-paths.outputs.apk-target-path }}
       test-apk-target-path: ${{ steps.determine-target-paths.outputs.test-apk-target-path }}

.github/workflows/update-e2e-fixtures.yml

@@ -180,7 +180,7 @@ jobs:
   update-fixtures:
     name: Export & update fixtures
     needs: [prepare]
-    runs-on: ghcr.io/cirruslabs/macos-runner:tahoe
+    runs-on: ${{ startsWith(github.base_ref, 'release/') && fromJSON('["ghcr.io/cirruslabs/macos-runner:tahoe"]') || fromJSON('["ghcr.io/cirruslabs/macos-runner:tahoe", "low-priority"]') }}
     timeout-minutes: 30
 
     env: