Fix ABI3 wheels warnings

[giampaolo]

Since a recent upgrade of abi3audit CI builds started failing because long time ago I defined some custom Py* functions which I use pretty much all over the C extension code (>200 occurrences). abi3audit does not recognize them as known cPython API symbols due to the fact that I used a Py* prefix, so let's rename these functions.

Also see pypa/abi3audit#111.

$ python3 -m abi3audit --verbose  dist/*-abi3-*.whl
[10:26:14] 👎 psutil-6.0.1-cp310-abi3-linux_x86_64.whl: _psutil_linux.abi3.so has non-ABI3 symbols                                              
           ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓                                                                                                  
           ┃ Symbol                          ┃                                                                                                  
           ┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩                                                                                                  
           │ PyInit__psutil_posix            │                                                                                                  
           │ PyErr_SetFromOSErrnoWithSyscall │                                                                                                  
           └─────────────────────────────────┘                                                                                                  
           👎 psutil-6.0.1-cp310-abi3-linux_x86_64.whl: _psutil_posix.abi3.so has non-ABI3 symbols                                              
           ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓                                                                                                  
           ┃ Symbol                          ┃                                                                                                  
           ┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩                                                                                                  
           │ PyErr_SetFromOSErrnoWithSyscall │                                                                                                  
           └─────────────────────────────────┘                                                                                                  
           💁 psutil-6.0.1-cp310-abi3-linux_x86_64.whl: 2 extensions scanned; 0 ABI version mismatches and 3 ABI violations found