Decrease the amount of time performance testing takes in GitHub Actions

[desrosj]

What problem does this address?

The Performance Tests workflow is the longest running test workflow by far, taking anywhere from 45 minutes to 2 hours.

Let's look at ways to speed this up.

What is your proposed solution?

It seems there are two groups of performance tests that currently run: post-editor and site-editor. If these could be run in parallel, that would potentially cut the time to run in half.

[desrosj]

Another aspect to think about. The workflow is required to complete for a PR to be allowed to merge. However, this workflow should not necessarily always be required. For example, if only .github/workflow/*.yml files are edited, then this isn't really needed (unless the actual performance.yml file is updated).

I'm sure there are other scenarios where this could be skipped entirely as well.

[Mamaduka]

We can also skip or make the action optional for the docs directory. The changes there can't affect the Editor(s) performance.

[desrosj]

Another observation I had today as it relates to caching.

The performance testing runs npm install multiple times to ensure that the needed dependencies and versions are installed each time a new branch is compared. But, the same cache key is used for the performance workflow as all other workflows. It's possible that the caching benefits are not being experienced in this situation.