Add WPT for the length of router rules

This CL will add test to ensure the router registration will fail if
the length of router rules exceeds the limit, which is currently 256.

Bug: 1519727, 40943429
Change-Id: Id849ddcd08dc5f246436471db60b9dcc71d2324a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5348571


Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Minoru Chikamune <chikamune@chromium.org>
Commit-Queue: Shunya Shishido <sisidovski@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1269937}