CI Task: feature branch specific CI pipeline

[sklam]

I have used git tricks to preserve history for azure ci changes. For example: 0fc40ca. This can be confusing. Instead, we can explore branch specific CI pipeline that only triggers for the feature branch so that we don't need to modify the default testing scripts.

If this doesn't work as nicely as we hoped, we will go for a two branches approach:

• one branch for changes merge-able to main
• one branch for testing

[sklam]

Just did the experiment on my fork.

I have two azure pipelines with different triggers.

• https://github.com/sklam/numba/tree/azure/main has azure-pipelines.yml is only triggered for azure/main branch.
• https://github.com/sklam/numba/tree/azure/specific has feature-azure-pipelines.yml is only triggered for azure/specific branch.

This is very doable.