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.
Subsequent invocations reset the trace. This removes the `tracing._reset` method.
Also fixed a bug where BASE element was not reset properly.
Also fixed a bug where tracing would affect the result of protocol call
by setting `callMetadata.error` property.
