RWW `W` via value not parsable by our via decoder

[bneradt]

I noticed while working on #9475 that neither our via string decoder website nor the traffic_via could parse the read while write W via cache result value. For example, a via string of cWs f results in a cache lookup value of undefined.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. Marking it stale to flag it for further consideration by the community.

[bryancall]

I am closing this as fixed. The read-while-write 'W' cache lookup result is now decoded by the via decoder. It was added to both the C++ and Perl traffic_via tools in #10924, which first shipped in release 10.0.0. A via string with 'W' in the cache lookup position now reports "in cache, fresh Read While Write (a cache HIT)" instead of an undefined value.