Update member.cpp to use fastcalls

[frmdstryr]

In the Member_set_x_mode functions cppy::replace does an XINCREF even though it's already checked.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.67%. Comparing base (9b80362) to head (bde09d9).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #231   +/-   ##
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  Coverage   97.67%   97.67%           
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  Files          24       24           
  Lines        1074     1074           
  Branches      162      162           
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  Hits         1049     1049           
  Misses         12       12           
  Partials       13       13           

[sccolbert]

Most of this is a good change and is easy to reason about. I would prefer the changes to parse_mode_and_context to be a separate change with a corresponding reason.

[frmdstryr]

Thanks for reviewing all these PRs! Hopefully it makes everyone's code a little faster.

The only other thing I can think of possibly updating yet would be changing any of the tp_call's to use vectorcallfunc but i'm not sure how to do that yet.