Add support for STM32H7R/Sxx parts

[emeb]

Detailed description

This change adds new support for the STM32H7R/S family of parts. Although these parts are STM32H7, there are
some differences in the IDs, number of banks and sector sizes as well as the register addresses and bit layouts that make supporting them with the current STM32H7 driver more complex than simply adding a separate driver so that's the approach taken here.

This change is co-authored by zyp who did the initial work. I've updated it for the latest API, made some cleanups
and got a few small details working that had been commented out. Thanks also to dragonmux and ALTracer for invaluable help in coming up to speed on the details.

Your checklist for this pull request

• [ x] I've read the Code of Conduct
• [ x] I've read the guidelines for contributing to this repository
• [ x] It builds for hardware native (see Building the firmware)
• [ x] It builds as BMDA (see Building the BMDA)
• [ x] I've tested it to the best of my ability
• [ x] My commit messages provide a useful short description of what the commits do

Closing issues

None

[emeb]

Looks like 3 CI failures - two are ROM overflows, but I'm guessing the 'pre-commit' is about code formatting?

[dragonmux]

Correct - lint / pre-commit is shouting about clang-format things. Please also note the contribution guideline about commit suffixing - in this case, mostly stm32h7rs: .

[emeb]

I've corrected the formatting problems and revised the commit messages to include the new target name. The CI failures currently appear to fall into two categories: 1) ROM overflows, and 2) Some sort of mingw CI problem unrelated to my sources.