fs: change write_begin/write_end interface to take struct kiocb *

fs: change write_begin/write_end interface to take struct kiocb *

Change the address_space_operations callbacks write_begin() and
write_end() to take struct kiocb * as the first argument instead of
struct file *.

Update all affected function prototypes, implementations, call sites,
and related documentation across VFS, filesystems, and block layer.

Part of a series refactoring address_space_operations write_begin and
write_end callbacks to use struct kiocb for passing write context and
flags.

Signed-off-by: Taotao Chen <chentaotao@didiglobal.com>
Link: https://lore.kernel.org/20250716093559.217344-4-chentaotao@didiglobal.com
Signed-off-by: Christian Brauner <brauner@kernel.org>