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.