md: add new helpers to suspend/resume and lock/unlock array

The new helpers suspend the array first and then lock the array,

Prepare to refactor from:

mddev_lock/lock_nointr
mddev_suspend
...
mddev_resuem
mddev_lock

With:

mddev_suspend_and_lock/lock_nointr
...
mddev_unlock_and_resume

After all the use cases is refactored, mddev_suspend/resume() will be
removed.

And mddev_suspend_and_lock() will also replace mddev_lock() for the case
that the array will be reconfigured, in order to synchronize with io to
prevent problems in many corner cases.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231010151958.145896-6-yukuai1@huaweicloud.com