Updates and backports to 4-3-stable

[MSP-Greg]

Description

Update 4-3-stable for use with Ruby 3 (3.0, 3.1, head)

Note that the minissl.c backports are not needed to get CI passing, but are either fixes or updates for tighter SSL configuration. Hence, I can remove the last commit...

EDIT: The last commit does not contain any updates for OpenSSL 3.0.

Closes #2824

Your checklist for this pull request

• I have reviewed the guidelines for contributing to this repository.
• I have added (or updated) appropriate tests if this PR fixes a bug or adds a feature.
• My pull request is 100 lines added/removed or less so that it can be easily reviewed.
• If this PR doesn't need tests (docs change), I added [ci skip] to the title of the PR.
• If this closes any issues, I have added "Closes #issue" to the PR description or my commit messages.
• I have updated the documentation accordingly.
• All new and existing tests passed, including Rubocop.

[nateberkopec]

Cheers, thanks Greg