ceph: convert ceph_zero_partial_page() to use a folio

Retrieve a folio from the pagecache instead of a page and operate on it. 
Removes several hidden calls to compound_head() along with calls to
deprecated functions like wait_on_page_writeback() and find_lock_page().

[dan.carpenter@linaro.org: fix NULL vs IS_ERR() bug in ceph_zero_partial_page()]
  Link: https://lkml.kernel.org/r/685c1424.050a0220.baa8.d6a1@mx.google.com
Link: https://lkml.kernel.org/r/20250612143443.2848197-5-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Alex Markuze <amarkuze@redhat.com>
Cc: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>