bcachefs: fsck: Improve check_key_has_inode()

bcachefs: fsck: Improve check_key_has_inode()

Print out more info when we find a key (extent, dirent, xattr) for a
missing inode - was there a good inode in an older snapshot, full(ish)
list of keys for that missing inode, so we can make better decisions on
how to repair.

If it looks like it should've been deleted, autofix it. If we ever hit
the non-autofix cases, we'll want to write more repair code (possibly
reconstituting the inode).

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>