net/mlx5: DR, Refactor ste_ctx handling for STE v0/1

As preparation for supporting ConnectX-7, this patches changes handling
of ste_ctx handling for existing STE v0 and V1:
 - each context is now a static struct, and it has a corresponding getter
 - v0 and v1 were extended to contain the fields that are required for
   integrating STEv2.

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>