btrfs: zlib: introduce zlib_compress_bio() helper

btrfs: zlib: introduce zlib_compress_bio() helper

The new helper has the following enhancements against the existing
zlib_compress_folios()

- Much smaller parameter list

  No more shared IN/OUT members, no need to pre-allocate a
  compressed_folios[] array.

  Just a workspace and compressed_bio pointer, everything we need can be
  extracted from that @cb pointer.

- Ready-to-be-submitted compressed bio

  Although the caller still needs to do some common works like
  rounding up and zeroing the tailing part of the last fs block.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>