RDMA/core: Add pinned handles to FRMR pools

RDMA/core: Add pinned handles to FRMR pools

Add a configuration of pinned handles on a specific FRMR pool.
The configured amount of pinned handles will not be aged and will stay
available for users to claim.

Upon setting the amount of pinned handles to an FRMR pool, we will make
sure we have at least the pinned amount of handles associated with the
pool and create more, if necessary.
The count for pinned handles take into account handles that are used by
user MRs and handles in the queue.

Introduce a new FRMR operation of build_key that allows drivers to
manipulate FRMR keys supplied by the user, allowing failing for
unsupported properties and masking of properties that are modifiable.

Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Reviewed-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20260226-frmr_pools-v4-5-95360b54f15e@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>