Split from #61682 and #60490 (as requested by @idryomov)

My implicit suggestion was to split by component (RADOS, RBD, CephFS, etc), not by source directory. Anything is fine here since this just massages includes, but I wanted to clarify for the future -- PRs that touch only a single component often move faster because there is less coordination involved.

My implicit suggestion was to split by component (RADOS, RBD, CephFS, etc), not by source directory.

Yes, I understood that, and that's what I've been trying to do all along. PR #61608 only got unrelated commits because it turned out that it caused build failures in other components that needed to be fixed prior to merging it; and adding the fixup commits for these other components was just an intermediate experiment to see if that's enough to make the CI happy.

jenkins test make check

CephFS bits were approved by @batrick in #61608, merging.