Remove legacy tracing

[sentrivana]

Remove the Transaction and Span and NoOpSpan classes (likely the whole tracing.py file). Remove legacy tracing functions and attributes from scope.py. Rename streamed versions of functions in scope.py (start_streamed_span → start_span, etc.). Remove any options, constants, etc. only used in transaction-based tracing (e.g. max span limits, etc.).

[linear-code]

PY-2655

[mgaligniana]

Hi @sentrivana! I was about to start working on #6975 to take the opportunity to get familiar with the tests but I think starting with this will make the rest of the work easier because it will end up removing a lot of code/tests. Unless an employee has already been assigned*