ext2: Convert ext2_unlink() and ext2_rename() to use folios

This involves changing ext2_find_entry(), ext2_dotdot(),
ext2_inode_by_name(), ext2_set_link() and ext2_delete_entry() to
take a folio.  These were also the last users of ext2_get_page() and
ext2_put_page(), so remove those at the same time.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230921200746.3303942-8-willy@infradead.org>