btrfs: use folios for reading super blocks from the block device

btrfs: use folios for reading super blocks from the block device

btrfs_read_disk_super() and the zoned super block log comparison go
through read_cache_page_gfp() and page_address(), and
btrfs_release_disk_super() recovers the page with virt_to_page(). Use
mapping_read_folio_gfp(), folio_address(), and virt_to_folio() instead.
This removes the last callers of read_cache_page_gfp() and put_page()
in btrfs.

Compute the super block address with offset_in_folio() as
write_dev_supers() does, rather than assuming it is at the start of
the page.

Assisted-by: Claude:claude-fable-5-1
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>