This change ensure's the HAR file is saved at `recordHar.path` on the
client instead of the server.
NB: The goal was to make this change transparent to the user and NOT
introduce any new APIs. Namely, I want to leave the API open for
potential `context.har.start()` and `context.har.stop()`.
This does BREAK servers that expect the HAR to be at the `recordHar.path`
on the server, but I think that's OK since there haven't been reports
of missing HAR on client making me think not many users are getting
HAR with client and server on different hosts anyways.
Closes#8355
chore: migrate tracing to har
- `HarTracer` is used by both `HarRecorder` that implements
`recordHar` context option, and by tracing.
- We keep the `trace.network` format for now, so it is not
yet a valid har file, but it contains har entries.
