gh-155525: Cover quadratic f-string tokenization regression

[gwosti]

Add regression coverage for modules containing many f-string or t-string replacement fields, expression text after tokenizer buffer growth, and != followed by a format specifier.

The tokenizer refactor in gh-156484 already removed the quadratic copying on main. This PR now retains that implementation and adds the original regression tests. The release-branch backports also need the original expression-span fix, adapted to their older tokenizer layout.

Closes gh-155525.

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[miss-islington-app]

Thanks @gwosti for the PR, and @pablogsal for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

[bedevere-app]

GH-157828 is a backport of this pull request to the 3.15 branch.

[miss-islington-app]

Sorry, @gwosti and @pablogsal, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker c1df6843d36233ec1da71a1d5f9b74dd6ebc9b97 3.13

[bedevere-app]

GH-157829 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-157828 is a backport of this pull request to the 3.15 branch.

[bedevere-app]

GH-157829 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-157830 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Windows11 Non-Debug 3.13 (tier-1) has failed when building commit 3dcc324.

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/1419/builds/1334) and take a look at the build logs.
4. Check if the failure is related to this commit (3dcc324) 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/1419/builds/1334

Failed tests:

• test_int

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "b:\uildarea\3.13.ware-win11.nondebug\build\Lib\test\test_int.py", line 729, in test_denial_of_service_prevented_str_to_int
    self.assertLessEqual(sw_fail_huge.seconds, sw_convert.seconds/2)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0.015625 not less than or equal to 0.0078125


Traceback (most recent call last):
  File "b:\uildarea\3.13.ware-win11.nondebug\build\Lib\test\test_int.py", line 740, in test_denial_of_service_prevented_str_to_int
    self.assertLessEqual(sw_fail_extra_huge.seconds, sw_convert.seconds/2)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0.015625 not less than or equal to 0.0078125