feat(celery): preserve original signature on apply_async wrapper for autospec compatibility

[JVenberg]

Summary

_wrap_task_run replaces Task.apply_async (and Celery.send_task) with a wrapper declared as:

@wraps(f)
def apply_async(*args, **kwargs):
    ...

functools.wraps copies __wrapped__ onto the wrapper, so inspect.signature resolves through it. But other introspection tools that do not follow __wrapped__ (e.g. inspect.getcallargs, IDE call-arg analysis, and some autospec-style test doubles built on __code__ rather than signature) see the wrapper's bare (*args, **kwargs) and lose the original parameter names.

This change adds:

try:
    apply_async.__signature__ = inspect.signature(f)
except (TypeError, ValueError):
    pass

after the wrapper is defined, making the wrapper signature-transparent to all introspection paths.

Precedent

PR #3178 (fix @sentry_sdk.tracing.trace changing function signature, fixing #3177) applied this exact pattern to func_with_tracing in sentry_sdk/tracing_utils.py. The _wrap_task_run wrapper has the same shape; this PR brings it in line.

Reproduction

import inspect
from celery import Celery
import sentry_sdk
from sentry_sdk.integrations.celery import CeleryIntegration

sentry_sdk.init(integrations=[CeleryIntegration()])

celery = Celery("repro")

@celery.task
def my_task(x, y):
    return x + y

from celery.app.task import Task

# Before this PR: getcallargs sees the bare (*args, **kwargs):
#   {'args': (None, (1, 2), {}), 'kwargs': {}}
# After this PR: getcallargs binds parameter names from the wrapped function:
#   {'self': None, 'args': (1, 2), 'kwargs': {}, 'task_id': None, ...}
print(inspect.getcallargs(Task.apply_async, None, (1, 2), {}))

Test

Added test_wrap_task_run_preserves_signature in tests/integrations/celery/test_celery.py. The test fails on master (sees args/kwargs placeholders) and passes with the fix (sees self, args, kwargs bound by name).

Why this matters downstream

At Rover.com (rover.com, ~1M+ DAU pet-services marketplace), our test suite defaults every mock.patch to autospec=True, spec_set=True (1,046 test files use this convention). With sentry-sdk 1.x we carry a FixSentryCeleryIntegration integration that wraps the private _wrap_apply_async symbol just to force wrapper.__signature__ = inspect.signature(<*args, **kwargs callable>). The same symbol exists in 2.x as _wrap_task_run, with the same gap. If this PR lands, that Rover-side monkey-patch can be deleted entirely on the next upgrade.

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General Notes

Filed without a pre-existing GitHub issue per the contribution guidelines note; happy to open one and reference it if maintainers prefer. PR is opened as a draft per the contribution standards.