net/mlx5: fs, add HWS modify header API function

Add modify header alloc and dealloc API functions to provide modify
header actions for steering rules. Use fs hws pools to get actions from
shared bulks of modify header actions.

Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20250109160546.1733647-7-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>