[ci] delete generate-test-matrix
Today, we have two pieces that conspire to determine what workflows we run:
- `generate_ci_workflows.py`, which takes a declarative description of what we want the workflow to do and uses jinja to generate a workflow yaml file
- `generate-test-matrix`, which runs at CI time to dynamically generate test jobs.
This is bad:
- Having one layer of code generation is unfortunate, having two is confusing.
- You cannot tell from a workflow yaml file what test jobs will be run.
- We have to do this careful dance of plumbing the args to `generate-test-matrix` through setting env vars and other such ugliness.
- In cases where the build job fails and prevents `generate-test-matrix` from running, a ghost `test` job that doesn't actually exist noises up the HUD and our stats.
- A bunch of useless `generate-test-matrix` jobs (8 on PRs) noise up our signal.
As far as I can tell, this complexity is unnecessary--we have all the information we need to generate the build matrix statically. There does not appear to be an advantage in retaining generate-build-matrix, so I am removing `generate-test-matrix` to simplify the CI.
The *only* place where we were actually doing something dynamic is in our windows gpu workflow, where we would check at runtime whether the workflow was triggered from a PR or master and behave accordingly. This is more simply done by just having two separate workflows with different trigger conditions, which avoids the madness of needing to parse labels and forking the behavior dynamically, which has been a source of confusion in the past.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73001
