[RR7] Instrument client-side HydratedRouter

[chargome]

Description

We need to instrument the client router of RR, since the browserTracingIntegration is only creating navigation spans by listening on popstate changes – which is way too late for our server instrumentation to make sense.

Current state with browserTracingIntegration:

React Router in framework mode uses a HydratedRouter on the client.

This ticket is about finding out if we can reuse parts of our existing RR client-side instrumentation for this router and handle navigation timing correctly.