xfrm: Refactor migration setup during the cloning process

Previously, migration related setup, such as updating family,
destination address, and source address, was performed after
the clone was created in `xfrm_state_migrate`. This change
moves this setup into the cloning function itself, improving
code locality and reducing redundancy.

The `xfrm_state_clone_and_setup` function now conditionally
applies the migration parameters from struct xfrm_migrate
if it is provided. This allows the function to be used both
for simple cloning and for cloning with migration setup.

Test: Tested with kernel test in the Android tree located
      in https://android.googlesource.com/kernel/tests/


      The xfrm_tunnel_test.py under the tests folder in
      particular.
Signed-off-by: Chiachang Wang <chiachangwang@google.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>