GH-131498: Replace single-element arrays with scalars in bytecodes.c

[brandtbucher]

Also, mark some unused items as unused (and fix a bug in the cases generator that sometimes disallowed multiple unused names to occur in the same instruction).

• Issue: Top-of-stack caching in the interpreter #131498

[markshannon]

Nice cleanup, thanks.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot aarch64 Android 3.x (tier-3) has failed when building commit 40ae889.

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/#/builders/1594/builds/1983) and take a look at the build logs.
4. Check if the failure is related to this commit (40ae889) 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/#/builders/1594/builds/1983

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

Click to see traceback logs

remote: Enumerating objects: 27, done.        
remote: Counting objects:   3% (1/27)        
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remote: Counting objects: 100% (27/27), done.        
remote: Compressing objects:  10% (1/10)        
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remote: Compressing objects: 100% (10/10), done.        
remote: Total 14 (delta 13), reused 4 (delta 4), pack-reused 0 (from 0)        
From https://github.com/python/cpython
 * branch                    main       -> FETCH_HEAD
Note: switching to '40ae88988c61638ee8625e5c0ee73606ede307bb'.

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do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

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

HEAD is now at 40ae88988c6 GH-131498: Replace single-element arrays with scalars in bytecodes.c (GH-132615)
Switched to and reset branch 'main'

configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)
configure: WARNING: pkg-config is missing. Some dependencies may not be detected correctly.

In file included from ../../Python/ceval.c:1061:
../../Python/generated_cases.c.h:12125:13: warning: code will never be executed [-Wunreachable-code]
 12125 |             stack_pointer -= 3;
       |             ^~~~~~~~~~~~~
../../Python/generated_cases.c.h:12118:13: warning: code will never be executed [-Wunreachable-code]
 12118 |             stack_pointer -= 4;
       |             ^~~~~~~~~~~~~
../../Python/generated_cases.c.h:7435:13: warning: code will never be executed [-Wunreachable-code]
 7435 |             stack_pointer += -1;
      |             ^~~~~~~~~~~~~
3 warnings generated.

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../../configure: line 4059: pkg-config: command not found
configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)
configure: WARNING: pkg-config is missing. Some dependencies may not be detected correctly.

In file included from ../../Python/ceval.c:1061:
../../Python/generated_cases.c.h:12125:13: warning: code will never be executed [-Wunreachable-code]
 12125 |             stack_pointer -= 3;
       |             ^~~~~~~~~~~~~
../../Python/generated_cases.c.h:12118:13: warning: code will never be executed [-Wunreachable-code]
 12118 |             stack_pointer -= 4;
       |             ^~~~~~~~~~~~~
../../Python/generated_cases.c.h:7435:13: warning: code will never be executed [-Wunreachable-code]
 7435 |             stack_pointer += -1;
      |             ^~~~~~~~~~~~~
../../Python/fileutils.c:460:1: warning: unused function 'decode_current_locale' [-Wunused-function]
  460 | decode_current_locale(const char* arg, wchar_t **wstr, size_t *wlen,
      | ^~~~~~~~~~~~~~~~~~~~~
../../Python/fileutils.c:679:1: warning: unused function 'encode_current_locale' [-Wunused-function]
  679 | encode_current_locale(const wchar_t *text, char **str,
      | ^~~~~~~~~~~~~~~~~~~~~
2 warnings generated.
3 warnings generated.
../../Modules/_localemodule.c:148:1: warning: unused function 'is_all_ascii' [-Wunused-function]
  148 | is_all_ascii(const char *str)
      | ^~~~~~~~~~~~
1 warning generated.
../../Modules/_hacl/Lib_Memzero0.c:52:6: warning: "Your platform does not support any safe implementation of memzero -- consider a pull request!" [-W#warnings]
   52 |     #warning "Your platform does not support any safe implementation of memzero -- consider a pull request!"
      |      ^
../../Modules/_hacl/Lib_Memzero0.c:40:10: warning: unused variable 'len_' [-Wunused-variable]
   40 |   size_t len_ = (size_t) len;
      |          ^~~~
2 warnings generated.

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curl: (56) Recv failure: Connection reset by peer