gh-125434: Fix non-ASCII thread names in faulthandler on Windows

[vstinner]

Add _Py_DumpWideString() function to dump a wide string as ASCII. It supports surrogate pairs.

Replace _Py_EncodeLocaleRaw() with _Py_DumpWideString() in write_thread_name().

• Issue: Faulthandler output should include the thread name #125434

[vstinner]

Example:

import _thread
_thread.set_name('a \xe9 \u20ac \U0010abcd .')
import faulthandler
def f():
    faulthandler.dump_traceback()
f()

Output:

Current thread 0x00000ab8 [a \xe9 \u20ac \U0010abcd .] (most recent call first):
  File "C:\victor\python\main\x.py", line 5 in f
  File "C:\victor\python\main\x.py", line 6 in <module>

where \U0010abcd is encoded as a surrogate pair.