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/azure-pipelines.yml

@@ -15,8 +15,9 @@ stages:
   - template: templates/group_tests.yml
     parameters:
       build_number: $(Build.BuildNumber)
-      scenario: fedora-latest
+      distro: fedora-latest
       ansible_version: "-core"
+      skip_git_test: true
 
 # Fedora
 
@@ -26,8 +27,9 @@ stages:
   - template: templates/group_tests.yml
     parameters:
       build_number: $(Build.BuildNumber)
-      scenario: fedora-latest
+      distro: fedora-latest
       ansible_version: "-core <2.14"
+      skip_git_test: true
 
 # Fedora
 
@@ -37,19 +39,22 @@ stages:
   - template: templates/group_tests.yml
     parameters:
       build_number: $(Build.BuildNumber)
-      scenario: fedora-latest
+      distro: fedora-latest
       ansible_version: "-core >=2.14,<2.15"
+      skip_git_test: true
 
 # Galaxy on Fedora
 
 - stage: Galaxy_Fedora_Latest
   dependsOn: []
   jobs:
-  - template: templates/galaxy_tests.yml
+  - template: templates/group_tests.yml
     parameters:
       build_number: $(Build.BuildNumber)
-      scenario: fedora-latest
+      distro: fedora-latest
       ansible_version: "-core >=2.14,<2.15"
+      skip_git_test: true
+      test_galaxy: true
 
 # CentOS 9 Stream
 
@@ -59,8 +64,9 @@ stages:
   - template: templates/group_tests.yml
     parameters:
       build_number: $(Build.BuildNumber)
-      scenario: c9s
+      distro: c9s
       ansible_version: "-core >=2.14,<2.15"
+      skip_git_test: true
 
 # CentOS 8 Stream
 
@@ -70,16 +76,6 @@ stages:
   - template: templates/group_tests.yml
     parameters:
       build_number: $(Build.BuildNumber)
-      scenario: c8s
-      ansible_version: "-core >=2.14,<2.15"
-
-# CentOS 7
-
-- stage: CentOS_7
-  dependsOn: []
-  jobs:
-  - template: templates/group_tests.yml
-    parameters:
-      build_number: $(Build.BuildNumber)
-      scenario: centos-7
+      distro: c8s
       ansible_version: "-core >=2.14,<2.15"
+      skip_git_test: true