[3.5] CI: Fully sync workflows and actions with 3.x branch

[akien-mga]

Continuation of #98892, where in the end I only cherry-picked #98896 (like for 3.6), without realizing that it didn't include the rest of the sync with the full 3.x .github folder.

This is now a copy paste of 3.x's .github folder (+ misc/scripts/), with the following differences:

• Keep 3.5 base branch
• Keep Emscripten 3.1.14
• Don't add the Linux minimal template build, which relies on a number of fixes and improvements not made in that branch

The main rationale for doing this change, aside from keeping things in sync, is so that CI runs on old branches match the current "GHA" workflow grouping, instead of going back to splitting each platform in its own run.

This discrepancy is what brought back these in the Actions tab:

Once all old branches match the same "GHA" pattern, I'll remove those run logs to clean the view again and just have "GHA".