gh-106320: Move _PyUnicodeWriter to the internal C API

[vstinner]

Move also _PyUnicode_FormatAdvancedWriter().

CJK codecs and multibytecodec.c now define the Py_BUILD_CORE_MODULE macro.

• Issue: C API: Remove private C API functions (move them to the internal C API) #106320

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM Raspbian 3.x has failed when building commit 5ccbbe5.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/424/builds/4339) and take a look at the build logs.
4. Check if the failure is related to this commit (5ccbbe5) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/424/builds/4339

Summary of the results of the build (if available):

== Tests result: ENV CHANGED ==

426 tests OK.

10 slowest tests:

• test_venv: 10 min 9 sec
• test_largefile: 7 min 38 sec
• test_multiprocessing_spawn: 4 min 50 sec
• test_math: 4 min 29 sec
• test___all__: 3 min 44 sec
• test_tarfile: 3 min 33 sec
• test_concurrent_futures: 3 min 18 sec
• test_subprocess: 2 min 55 sec
• test_peg_generator: 2 min 26 sec
• test_cppext: 2 min 25 sec

1 test altered the execution environment:
test.test_asyncio.test_unix_events

19 tests skipped:
test.test_asyncio.test_windows_events
test.test_asyncio.test_windows_utils test_devpoll test_idle
test_ioctl test_kqueue test_launcher test_perf_profiler
test_startfile test_tcl test_tkinter test_ttk test_ttk_textonly
test_turtle test_winconsoleio test_winreg test_winsound test_wmi
test_zipfile64

Total duration: 37 min 46 sec

Click to see traceback logs

remote: Enumerating objects: 36, done.        
remote: Counting objects:   2% (1/36)        
remote: Counting objects:   5% (2/36)        
remote: Counting objects:   8% (3/36)        
remote: Counting objects:  11% (4/36)        
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remote: Counting objects:  22% (8/36)        
remote: Counting objects:  25% (9/36)        
remote: Counting objects:  27% (10/36)        
remote: Counting objects:  30% (11/36)        
remote: Counting objects:  33% (12/36)        
remote: Counting objects:  36% (13/36)        
remote: Counting objects:  38% (14/36)        
remote: Counting objects:  41% (15/36)        
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remote: Counting objects:  47% (17/36)        
remote: Counting objects:  50% (18/36)        
remote: Counting objects:  52% (19/36)        
remote: Counting objects:  55% (20/36)        
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remote: Counting objects:  94% (34/36)        
remote: Counting objects:  97% (35/36)        
remote: Counting objects: 100% (36/36)        
remote: Counting objects: 100% (36/36), done.        
remote: Compressing objects:  12% (1/8)        
remote: Compressing objects:  25% (2/8)        
remote: Compressing objects:  37% (3/8)        
remote: Compressing objects:  50% (4/8)        
remote: Compressing objects:  62% (5/8)        
remote: Compressing objects:  75% (6/8)        
remote: Compressing objects:  87% (7/8)        
remote: Compressing objects: 100% (8/8)        
remote: Compressing objects: 100% (8/8), done.        
remote: Total 19 (delta 18), reused 11 (delta 11), pack-reused 0        
From https://github.com/python/cpython
 * branch                  main       -> FETCH_HEAD
Note: switching to '5ccbbe5bb9a659fa8f2fe551428c84cc14015f44'.

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Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 5ccbbe5bb9 gh-106320: Move _PyUnicodeWriter to the internal C API (#106342)
Switched to and reset branch 'main'

./Modules/_testcapi/heaptype_relative.c: In function ‘make_sized_heaptypes’:
./Modules/_testcapi/heaptype_relative.c:62:28: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
   62 |                            (unsigned long long)data_ptr,
      |                            ^

make: *** [Makefile:2004: buildbottest] Error 3