Fix conflict with ddtrace futures patching by renaming fn parameter

[alexmojaki]

Fixes problem reported in https://pydanticlogfire.slack.com/archives/C06EDRBSAH3/p1737061346996829

Before this PR, this:

from concurrent.futures import ThreadPoolExecutor

from ddtrace.contrib.internal.futures.patch import patch

import logfire

# Removing one of these or changing the order will cause the error to disappear.
patch()
logfire.configure()

ThreadPoolExecutor().submit(lambda: None).result()

raises:

Traceback (most recent call last):
  File "/Users/alex/Library/Application Support/JetBrains/PyCharm2024.3/scratches/scratch_990.py", line 11, in <module>
    ThreadPoolExecutor().submit(lambda: None).result()
  File "/Users/alex/.pyenv/versions/3.12.6/lib/python3.12/concurrent/futures/_base.py", line 449, in result
    return self.__get_result()
           ^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.12.6/lib/python3.12/concurrent/futures/_base.py", line 401, in __get_result
    raise self._exception
  File "/Users/alex/.pyenv/versions/3.12.6/lib/python3.12/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/work/logfire/.venv/lib/python3.12/site-packages/ddtrace/contrib/internal/futures/threading.py", line 36, in _wrap_execution
    return fn(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^
TypeError: <lambda>() got an unexpected keyword argument 'carrier'

Executor.submit has the signature (self, fn, /, *args, **kwargs). Although fn is now positional-only, ddtrace pays special attention to that name in https://github.com/DataDog/dd-trace-py/blob/26dc258020126a7527f973c26494f0dd1016dead/ddtrace/contrib/internal/futures/threading.py#L7-L23

So avoiding that name does the trick.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (294aa41) to head (496464d).
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Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files          138       138           
  Lines        11044     11044           
  Branches      1565      1565           
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[nairb774]

Thanks for quickly fixing this - really appreciate it!