RustPython: Implement missing `cmath` functions

The following functions are currently missing:

• acos
• acosh
• asin
• asinh
• atan
• atanh
• cos
• cosh
• exp
• log
• log10
• sin
• sinh
• sqrt
• tan
• tanh

Inspiration for how their implementation might look can be found in Modules/cmathmodule.c (and Modules/clinic/cmathmodule.c.h for argument parsing) of the CPython codebase. Lib/src/stdlib/math.rs equivalent functions should also be roughly similar.

Note to contributors: due to the way tests are organized, you’ll need to add your function to the list of tested functions in the test_functions class attribute of CMathTests (on line 58 in Lib/tests/test_cmath.py). I.e, if you want to add log, add it alphabetically at the list used in the comprehension:

# add it to the list
test_functions = [getattr(cmath, fname) for fname in ['cos', ..., 'log', 'sqrt']]

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If anyone wants to pick a function or two up, leave a comment naming the functions so other people can see who’s working on what. Hopefully that will minimize conflicts.