Miscellaneous GEM back-end updates

This MR contains miscellaneous GEM updates, mainly DAQ-related but not only, gathered over an extended period of time and included in various builds and setups here and there. After almost 1 year - for the oldest commit -, it is finally time to upstream those changes in order to avoid further divergences.

Each commit individually describes in detail the changes brought in. The following points are however worth being noticed:

• Despite being based on devel, this branch is meant to fully work with top-ui-dev. It can be merged first or second, but only combined builds have been tested against hardware as of aeb33299.
• Commit 357d2be8 introduces a fix for commit d40bb66e in the top-ui-dev branch. Again, the merge order does not matter.
• Merging both devel and top-ui-dev introduces build-time bugs in some flavors of the firmware. Take example on https://gitlab.cern.ch/lpetre/0xbefe-online-ci/-/commits/release/rolling-testing/ - in particular, commits 2dd5f6e2, 17a261b7, and 4c433f87 - on how to fix those issues.

Regarding the testing, the changes have been included in GE1/1 data-taking at P5 for weeks (possibly months) as well as the ME0 stack setup from the last test beam. All reported issues have been fixed and the usage has been more than satisfactory.