ci: allow custom actions runner to be defined (#3989)

.github/workflows/REUSABLE_backend.yml

@@ -45,6 +45,12 @@ on:
         required: false
         default: error_reporting=E_ALL
 
+      runner_type:
+        description: The type of runner to use for the jobs. This should be one of the types supported by the `runs-on` keyword.
+        type: string
+        required: false
+        default: 'ubuntu-latest'
+
     secrets:
       composer_auth:
         description: The Composer auth tokens to use for private packages.
@@ -57,7 +63,7 @@ env:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ${{ inputs.runner_type }}
 
     strategy:
       matrix:
@@ -166,7 +172,7 @@ jobs:
           COMPOSER_PROCESS_TIMEOUT: 600
 
   phpstan:
-    runs-on: ubuntu-latest
+    runs-on: ${{ inputs.runner_type }}
 
     strategy:
       matrix:

.github/workflows/REUSABLE_frontend.yml

@@ -86,6 +86,12 @@ on:
         type: string
         required: false
 
+      runner_type:
+        description: The type of runner to use for the jobs. This should be one of the types supported by the `runs-on` keyword.
+        type: string
+        required: false
+        default: 'ubuntu-latest'
+
     secrets:
       bundlewatch_github_token:
         description: The GitHub token to use for Bundlewatch.
@@ -103,7 +109,7 @@ env:
 jobs:
   build:
     name: Checks & Build
-    runs-on: ubuntu-latest
+    runs-on: ${{ inputs.runner_type }}
 
     if: >-
       ((github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository) || github.event_name != 'pull_request')