net/mlx5: HWS, Generalize complex matchers

The existing solution of complex matchers splits the match parameters
across two, and exactly two, matchers. For some rather extreme cases
(e.g. IPv6-in-IPv6 tunnels), even two matchers are not enough.

Generalize complex matchers to up to 4 submatchers, and allow easy
extension to more if needed. This resulted in rewriting a large part
of the high-level complex matchers logic, but the original concepts
were rock solid and still hold.

Key characteristics of the new implementation:

* Rework complex matchers to include multiple submatchers. All
  submatchers but the first are isolated, in keeping with the existing
  paradigm of handing off to specialized matchers that are not otherwise
  reachable by regular rules.

* Similarly, rework complex rules to allow splitting them into more than
  two simple rules. Rules continue to be refcounted to allow for
  multiple complex rules matching on identical parts of the match
  params.

* Rely on the match tag, as opposed to the entire match_param, to hash
  subrules. This results in lower memory usage.

* Prefer to split the original user-supplied match parameters rather
  than the internal field descriptors. This avoids the awkward
  transition back and forth between the two formats.

* Allow splitting multi-dword fields across matchers. The only
  restrictions that the new implementation impose are: a) any fragment
  of an IP address must be accompanied by a match on the IP version; and
  b) a single lower dword of an IPv6 address cannot be present in a
  submatcher as it would be interpreted as an IPv4 address.

* Employ a greedy algorithm to split the match params, as opposed to
  complete search. The results are not optimal, but the algorithm is now
  linear compared to exponential. Consequently, we see complex matcher
  creation time drops two orders of magnitude in our tests.

Signed-off-by: Vlad Dogaru <vdogaru@nvidia.com>
Signed-off-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/1759094723-843774-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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