tokenize: `e.offset` on `IndentationError` is not set correctly

Bug report

Bug description:

import io, tokenize

input_s = """
def foo():
    x = 1
   x = "some_very_long_expression"
"""
try:
    list(tokenize.generate_tokens(io.StringIO(input_s).readline))
except IndentationError as e:
    print(f"{e.offset = }")

The line x = "some_very_long_expression" is indented with 3 spaces instead of 4, so we get an error.
We would expect the offset to be around 3, since that is where the issue is.
On python 3.12+, the offset is instead 35, equal to the length of the line + 1.

This appears to be caused by the refactor of tokenize done in 3.12 for PEP 701
Potentially related to https://github.com/python/cpython/issues/84515
Funnily enough, the exact same thing seems to have happened around 3.8 https://github.com/python/cpython/issues/75676

Tested versions:

Testing command:
nix-shell -p python311 --run "python --version && python tmp.py"
(and replace 311 by 312, 313, etc)

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Linked PRs

• gh-154281

Commencez par tokenize.generate_tokens et reproduisez l’exemple d’IndentationError fourni sur les versions de Python indiquées. Suivez la manière dont le tokenizer construit IndentationError et comparez l’offset avec le comportement de Python 3.11. C’est terminé lorsque la ligne mal indentée signale un offset proche de 3, avec une couverture de régression pour l’exemple.