Add and validate a dependent job for branch protection

[EliahKagan]

GitHub branch protection rules requiring CI checks currently only support listing individual checks as required.

This adds an all-pass job that depends on all other jobs, to simplify this. all-pass can thus be made a required check, in lieu of numerous others, which it takes care to ensure are treated as effectively required.

This also adds an all-pass-meta job that checks that the all-pass job really depends on all intended other jobs, which currently is all other jobs in the workflow. It is intentional at this time that neither CodeQL (configured via the "default" setup) nor the Markdown links check shall be blocking.

The all-pass job is based on the tests-pass job in gitoxide, introduced in GitoxideLabs/gitoxide#1551 by Jiahao XU (https://github.com/NobodyXu), moderately edited since, and further moderately edited in the form it appars here.

In view of...

• (de minimis) the small size of the code, other than the list of jobs it depends on, which is not duplicated since the jobs here differ including in their names, and

• how widespread that specific technique appears to be, based in part on searching GitHub and examining results with the exact string "contains(needs.*.result, 'cancelled')", and

• (scènes à faire) the limited number of reasonable feasible ways the technique can be expressed

...it seems to me that that continued resemblance of fragments of the code here to the code there does not raise copyright or related problems, in the all-pass job.

Separately, the all-pass-meta job is is a direct copy of the check-blocking job in gitoxide, introduced among other changes in GitoxideLabs/gitoxide#1668. The all-pass-meta job is a near-complete copy of check-blocking, with only minimal changes, and even keeps the comments naerly unchanged. Although check-blocking is less important than tests-pass, it is also significantly longer and more complex.

But unlike tests-pass, I contributed the check-blocking job in gitoxide (without copying from a previous work to do so; and licensing it nonexclusively, with no transfer or assignment of copyright). So that specific code is fine for me to reuse here.

More broadly, I intend that anyone be allowed to reuse the code of the all-pass-meta job (as it appears here), anywhere, with no restrictions. See the 0BSD license file that accompanies this (algorithms-python) project.

Note that the code of check-blocking in gitoxide may receive modifications authored by others, may be renamed, and some other job may be renamed to it, or it might be removed and some other job with that name may arise later, etc. Such code may still only be used under the terms that it is offered; these more permissive terms do not apply to such code, especially if it is written by others.