This adds a pw_router module for routing packets over network links.
Initially, this module contains a basic StaticRouter which uses a static
routing table.
Change-Id: I5534c7fec5c622e7af6548c48793ff7f7d6dd098
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/29440
Commit-Queue: Alexei Frolov <frolv@google.com>
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
