Clean up profiler interface in new major

[sentrivana]

Once we get rid of the transaction profiler, look at what would make sense to clean up. Ideas:

• move continuous_profiler to just profiler
• use the simpler option names that were in use by the transaction profiler for the continuous profiler instead
• …?

Make sure to call out all changes in the migration guide.

[linear-code]

PY-2635