Support function tracing in online mode of drmemtrace

Doesn't look like we have an existing feature request on this so creating one.

Function tracing is not supported in the online mode today. The reason seems to be the following[1]:
```
// Online is not supported as we have no mechanism to pass the funclist_file
// data to the simulator.
```

Xref the dynamorio-users discussion where this was requested: https://groups.google.com/g/dynamorio-users/c/dVuP3bv6zTs

[1]: https://github.com/DynamoRIO/dynamorio/blob/3fc09e86e560c5d9934268e8b213861ff4b3efed/clients/drcachesim/tracer/func_trace.cpp#L424