[C API] Python exports symbols without `Py` prefix

[vstinner]

Bug report

Bug description:

Python should only export symbols starting with Py prefix (or _Py prefix).

List found by Stefan:

bufferedrandom_spec
bufferedreader_spec
bufferedrwpair_spec
bufferedwriter_spec
bytesiobuf_spec
bytesio_spec
constevaluator_spec
fileio_spec
generic_spec
iobase_spec
nldecoder_spec
paramspecargs_spec
paramspeckwargs_spec
paramspec_spec
pkgcontext
PY_TIMEOUT_MAX     # I did not filter for PY with capital Y
rawiobase_spec
stringio_spec
textiobase_spec
textiowrapper_slots
textiowrapper_spec
typevar_spec
typevartuple_slots
typevartuple_spec

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-141376: Fix exported symbols #141377
• gh-141376: Rename _AsyncioDebug to _Py_AsyncioDebug #141391
• gh-141376: Remove exceptions from make smelly #141392
• gh-141376: make smelly: List all symbols, repeat smelly ones at end #141394
• gh-141376: Check also for data in make smelly #141397