Issue #3194401: Switch to CircleCI as the default automated testing platform

.circleci/config.yml

 version: 2.1
 orbs:
   browser-tools: circleci/browser-tools@1.1  
-executors:
-  varbase-build:
-    docker:
-      - image: circleci/php:7.3-apache-stretch-node-browsers
-        auth:
-          username: mydockerhub-user
-          password: $DOCKERHUB_PASSWORD
-      - image: circleci/mysql:8.0.4
-        auth:
-          username: mydockerhub-user
-          password: $DOCKERHUB_PASSWORD
-        entrypoint: ['docker-entrypoint.sh', '--default-authentication-plugin=mysql_native_password']
-        environment:
-          MYSQL_ROOT_PASSWORD: rootpw
-          MYSQL_DATABASE: test_varbase
-          MYSQL_USER: user
-          MYSQL_PASSWORD: passw0rd
-    working_directory: /var/www/html/varbase/docroot
+defaults: &defaults
+  docker:
+    - image: circleci/php:7.3-apache-stretch-node-browsers
+      auth:
+        username: mydockerhub-user
+        password: $DOCKERHUB_PASSWORD
+    - image: circleci/mysql:8.0.4
+      auth:
+        username: mydockerhub-user
+        password: $DOCKERHUB_PASSWORD
+      entrypoint: ['docker-entrypoint.sh', '--default-authentication-plugin=mysql_native_password']
+      environment:
+        MYSQL_ROOT_PASSWORD: rootpw
+        MYSQL_DATABASE: test_varbase
+        MYSQL_USER: user
+        MYSQL_PASSWORD: passw0rd
+  working_directory: /var/www/html/varbase/docroot
 
 jobs:
   varbase-setup:
     resource_class: small
-    executor: varbase-build
+    <<: *defaults
     steps:
       - checkout:
           path: /var/www/html/varbase
@@ -163,7 +162,7 @@ jobs:
             drush cr
   varbase-testing:
     resource_class: small
-    executor: varbase-build
+    <<: *defaults
     parallelism: 4
     steps:
       ## Automated Functional Acceptance Testing group - 01 website base requirements