[WIP] [mypyc] Refactor name generation in Load/InitStatic

[TH3CHARLie]

related mypyc/mypyc#737

This PR aims to refactor the name generation/mangling logic in LoadStatic and InitStatic from codegen to IR build.

• prefix
• lib_prefix
• private names(suffix)

[TH3CHARLie]

Well, NameGenerator is the big issue here, it's related to the code generation context.

Also, what's the ideal granularity of a name generated by irbuild? For example, loading a static float will have an identifier of float_3 now. With the existing part of this PR, we'll have an identifier of float_3 and a prefix of CPyStatic_. Its final name would be CPyStatic_float_3 because its module and group would all be empty.

And also, it is a bit strange to me that a static variable is not marked with C keyword static but only with the prefix. I plan to introduce this modification in codegen in this PR. So eventually the code will be static PyObject *CPyStatic_float_7; when initializing the globals.

[TH3CHARLie]

a related PR merged: #8973, so close this