CTest follow-up: add GitHub Actions workflow for checksum comparisons with machine-precision tolerance

[EZoni]

Once #5256 will have made available more tolerances for the checksums comparisons, we want to add a new GitHub Actions workflow that does the following:

1. check out development
2. compile
3. run CTest and reset checksums
4. merge current branch into development
5. re-compile
6. re-run CTest and compare checksums with machine-precision tolerance

We also need to document how to run the equivalent of this locally.