Updating CI-CD pipelines ymls

Following changes are made:

In .gitlab-ci.yml file:

1. Included standard-setup.yml to do standard setup of the pipeline
2. Included ci-cd-pipelines/build/python.yml to set up compile and unit test stages
3. Included azure.yml to set up azure specific stages
4. Added few variables

Also,

1. Added new file devops/azure/override-stages.yml: Currently, it is overriding all the stages of azure.yml with dummy stages as pipeline setup is not complete yet. Going forward it will override containerize and test stages only. Additional jobs can be added here on requirement.

Some more information: Few stages cannot be completed yet as unit tests, azure helm charts and integration tests are not complete yet. Therefore, dummy stages have been added for them.

Passed run for the added pipeline can be found here