btrfs: remove folio ordered flag and subpage bitmap

btrfs: remove folio ordered flag and subpage bitmap

Btrfs has an internal flag/subpage bitmap called ordered, which is to
indicate that a block has corresponding ordered extent covering it.

However this requires extra synchronization between the inode ordered
tree, and the folio flag/subpage bitmap, not to mention we need to
maintain the extra folio flag with subpage bitmap.

As a step to align btrfs_folio_state more closely to iomap_folio_state,
remove the btrfs specific ordered flag/bitmap.

This will also save us 64 bytes for the bitmap of a huge folio.

Since we're here, also update the ASCII graph of the bitmap, as there
are only 3 sub-bitmaps now, show all sub-bitmaps directly.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>