CI: Squash commits from cross-compile pipeline + update actions and runners versions

[pietrygamat]

A small improvement to cross-compilation pipeline. It now generates a branch with a single commit with all precompiled binaries, instead of one commit per architecture.

E.g. https://github.com/pietrygamat/jssc/commits/single-commit-natives-precompiled-natives.

[tresf]

No objections.

A word on ubuntu-latest:

• Note, when you do things like ubuntu-latest versus ubuntu-20.04, it means that when a dependency name changes, our CI will fail. This is fine with me, because latest prevents the action from bitrot and is arguably easier than trying to remember which LTS releases are still supported by GitHub.
• Another caution... for larger projects... binaries created with ubuntu-latest may suffer regressions. This is best explained here.
• Our binaries are quite simple and the ones we distribute are built using docker, so this is not as much of a concern, but wanted to mention this.

In regards to merging, I will ask you to do so at your leisure.