Merge patch series "Remove aops->writepage"

Matthew Wilcox (Oracle) <willy@infradead.org> says:

We have just one filesystm (vboxsf) left which implements ->writepage.
This patchset converts it to writepages then removes all the callers
of ->writepage.

* patches from https://lore.kernel.org/r/20250402150005.2309458-1-willy@infradead.org:
  fs: Remove aops->writepage
  mm: Remove swap_writepage() and shmem_writepage()
  ttm: Call shmem_writeout() from ttm_backup_backup_page()
  i915: Use writeback_iter()
  shmem: Add shmem_writeout()
  writeback: Remove writeback_use_writepage()
  migrate: Remove call to ->writepage
  vboxsf: Convert to writepages
  9p: Add a migrate_folio method

Link: https://lore.kernel.org/r/20250402150005.2309458-1-willy@infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>