[InputVizard] Implement hang renderer detection in Viz.

This CL introduces new mojo methods in RenderInputRouterDelegate to
allow browser to notify RenderInputRouters in Viz to restart their input
event ack timers. This is useful when a RenderWidget becomes visible
again or when the user decides to wait on a hung page. This CL also
notifies browser when input event ack timeout occurs on Viz (because of
no acks being received on Viz) allowing it to take action if the
renderer is unresponsive.  Furthermore, the
RenderInputRouterDelegateClient interface is used to inform the browser
about changes in the renderer's responsiveness state.

Doc link:

https: //docs.google.com/document/d/1J7bDpHFcMvyQZtj9CHuKVH_wGLlxb2GqbF8qW82gUQA/edit?usp=sharing
Change-Id: Ice49b16fff6077a4f3d2a83190c303731d3c9c76
Bug: b:391135801
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6198701
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Commit-Queue: Aman Verma <amanvr@google.com>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1456233}