gh-109596: Ensure repeated rules in the grammar are not allowed and fix incorrect soft keywords

[pablogsal]

• Issue: Rule name conflict and token marking mistakes in the 3.12.0rc grammar #109596

[pablogsal]

@Yhg1s Not sure if you want to include this in 3.12.0, but it incorrectly shows : and = as soft keywords otherwise. The other rule is not used anywhere

[Yhg1s]

Considering there isn't any bad behaviour (as far as I can tell) from this, I'll defer it until 3.12.1.

[miss-islington]

Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington]

Sorry, @pablogsal, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker b28ffaa193efc66f46ab90d383279174a11a11d7 3.12

[bedevere-app]

GH-109752 is a backport of this pull request to the 3.12 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM Raspbian 3.x has failed when building commit b28ffaa.

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/4987) and take a look at the build logs.
4. Check if the failure is related to this commit (b28ffaa) 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/4987

Failed tests:

• test.test_concurrent_futures.test_shutdown
• test_socket

Failed subtests:

• test_interpreter_shutdown - test.test_concurrent_futures.test_shutdown.ProcessPoolSpawnProcessPoolShutdownTest.test_interpreter_shutdown

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/test/test_concurrent_futures/test_shutdown.py", line 49, in test_interpreter_shutdown
    self.assertFalse(err)
AssertionError: b'Exception in thread Thread-1:\nTraceback (most recent call last):\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/threading.py", line 1059, in _bootstrap_inner\n    self.run()\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/concurrent/futures/process.py", line 344, in run\n    self.add_call_item_to_queue()\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/concurrent/futures/process.py", line 399, in add_call_item_to_queue\n    self.call_queue.put(_CallItem(work_id,\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/multiprocessing/queues.py", line 94, in put\n    self._start_thread()\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/multiprocessing/queues.py", line 177, in _start_thread\n    self._thread.start()\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/threading.py", line 978, in start\n    _start_new_thread(self._bootstrap, ())\nRuntimeError: can\'t create new thread at interpreter shutdown\nTraceback (most recent call last):\n  File "<string>", line 1, in <module>\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/multiprocessing/spawn.py", line 122, in spawn_main\n    exitcode = _main(fd, parent_sentinel)\n               ^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/multiprocessing/spawn.py", line 132, in _main\n    self = reduction.pickle.load(from_parent)\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File "/var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/Lib/multiprocessing/synchronize.py", line 115, in __setstate__\n    self._semlock = _multiprocessing.SemLock._rebuild(*state)\n                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\nFileNotFoundError: [Errno 2] No such file or directory\n' is not false