Make GitHub pipeline run tests on multiple node versions

[giseburt]

This comes from the discussion on #3447, where (in that case) been able to build with different combinations of node and ESM would be useful.

The concept being to use jobs.<job_id>.strategy.matrix int he GitHub workflows as outlined here: Using a matrix for your jobs

This is a generic capability projen projects should be able to utilize as well, and there's already partial support for in place.

I'm working on a PR for this, and it turns out it's not as well supported as it at first appears.

Issue's I've encountered (so far, checked means I'm past that in my in-progress PR):

• BuildWorkflow doesn't expose a way to set the strategy in it's options, and there's no mechanism (outside of an escape-hatch) to set it later
• NodeProject doesn't expose a way to set the strategy of the build workflow
  • I've added it as buildWorkflowJobStrategy to match buildWorkflowTriggers etc.
  • This only covers build workflow, what if we want workflow matrices for other jobs such as release? I'd assume they wouldn't be the same matrix
• JobMatrixValue doesn't support objects
  • Docs linked to above say:

    A variable configuration in a matrix can be an array of objects.

  • It's unclear if that means it can be arbitrarily deep objects, so I'm going with a two-level
• For node version I've added buildWorkflowNodeVersion and wired it up to override node version in the workflow setup for the build workflow
• We build and test in the same step, and then release an artifact from that build. We either need a mechanism to choose which build is the one that's released or we need to separate build and test
  • Closely related, we probably don't need or want "Upload coverage to Codecov" on every node of the matrix
  • Update: Added ability to set a variable to control that additional steps

I'm stopped on that last part, and am open to suggestions. For now, I'm going to add a property with node 18.14.2 (current one being used to release) that I'll have it add if statements to the final "Backup artifact permissions" and "Upload artifact" steps.

I'll update when I have a branch pushed to review.

Update: PR in #3500