Update test workflow to run lighter testing on draft PRs

[ehennestad]

Motivation

This PR introduces a few changes to improve CI speed and efficiency:

• Run tests only on the latest MATLAB release when a pull request is in draft mode (i.e., no version matrix).
• Cache MATLAB setup and Python dependencies to reduce setup time.
• All tests still run — none are skipped.

Testing across all supported MATLAB releases can occasionally take significantly longer than usual (e.g., 27 minutes vs. the typical 12), especially when workers are queued or run slower than usual. These changes aim to make draft PR iterations faster while retaining full test coverage once the PR is marked ready for review.

How to test the behavior?

N/A

Checklist

• Have you ensured the PR description clearly describes the problem and solutions?
• Have you checked to ensure that there aren't other open or previously closed Pull Requests for the same change?
• If this PR fixes an issue, is the first line of the PR description fix #XX where XX is the issue number?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.08%. Comparing base (16862b7) to head (6008c84).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #720      +/-   ##
==========================================
+ Coverage   95.05%   95.08%   +0.02%     
==========================================
  Files         161      162       +1     
  Lines        5868     5897      +29     
==========================================
+ Hits         5578     5607      +29     
  Misses        290      290              

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[bendichter]

Is this to get the tests to run faster? What tests are being skipped? How long does it take to run the tests before and after the change?

[ehennestad]

A few changes to speed things up:

1. only run tests with latest matlab release (no matrix) if PR is in draft mode

2. cache matlab setup and python dependencies

No tests are skipped

Sometimes testing on all releases can take more time than usual (ie if some workers are queued or for other reasons take longer to finish) last week a test run took 27 min compared to usual 12.

Caching saves about 1 minute

[ehennestad]

Based on discussion:

• Added more comments in the set-matrix workflow job
• Removed the part adding EOF before and after a json string
• Removed caching for pip dependencies. No noticable speedup + risk of using oudated versions of dependencies