upstream CI: Simplify pipelines enviroment creation

Several optimizations have been done to the pipelines, to make them
closer to what can be reproduced, with the existing scripts, in a
development environment:

- Use start.sh and build.sh scripts to build and start containers
- Use variables to configure different stages instead of using separate
  files
- Use a commom 'prepare_environment' to create the environment for every
  pipeline
- Use a single file defining testing steps (run_tests.yml)
- Remove Centos 7 pipelines
- Reduce the number of pipelines in the test matrix due to the amount of
  time that tests were using
- Use Azure "loop" (each) to create test groups

The above changes make the pipelines easier to understand and modify.

infra/azure/templates/prepare_environment.yaml

@@ -0,0 +1,30 @@
+---
+parameters:
+  - name: distro
+    type: string
+    default: fedora-latest
+  - name: ansible_version
+    type: string
+    default: ""
+  - name: python_version
+    type: string
+    default: 3.x
+  - name: build_number
+    type: string
+
+steps:
+  - task: UsePythonVersion@0
+    inputs:
+      versionSpec: '${{ parameters.python_version }}'
+
+  - script: |
+      pip install "ansible${{ parameters.ansible_version }}" -r requirements-tests.txt
+    retryCountOnTaskFailure: 5
+    displayName: Install test dependencies
+
+  - script: ansible-galaxy collection install -r requirements-podman.yml
+    retryCountOnTaskFailure: 5
+    displayName: Install Ansible collections
+
+  - script: infra/image/start.sh ${{ parameters.distro }}-server
+    displayName: Setup target container for ${{ parameters.distro }}