Allow attaching co_firstlineno to frame name

[Jongy]

Before this PR, we had 2 modes:

• --function NOT passed: attach the line number from frame->f_lasti to the frame name
• --function passed: do not attach any line number

The main reason to avoid attaching f_lasti is to have frames aggregated by the function name only;
so different "lines" of the same function are aggregated as a single frame.

However, line numbers are useful as identifiers for functions, especially in large files / for common
function names such as "init", which are likely to appear multiple times in the same file.
This PR allows attaching code->co_firstlineno instead, which can serve to help in identification,
while not preventing frames of the same function from being aggregated together.

After this PR, we have these options:

• --function, --nolineno NOT passed: same as before - attach f_lasti to the frame name
• --function passed: attach co_firstlineno to the frame name
• --nolineno: do not attach any line number (also, do not spend time on retrieving the line number from
  the remote process).

Closes: #424

I have tested it on --format raw and AFAICT the lineno option will remain the default for e.g the py-spy top mode, perhaps we want to add it there as well?

@benfred do you think this deems any module-level tests added? I can add

[Jongy]

@benfred , is it missing anything?

[benfred]

thanks for this!