fix: Replace asyncio.iscoroutinefunction with compatibility shim for Python 3.16

[Dibbu-cell]

Description

This PR fixes the deprecation warning for asyncio.iscoroutinefunction that will be removed in Python 3.16. The function was deprecated in Python 3.12 in favor of inspect.iscoroutinefunction.

Issues

• resolves: #4900

Reminders

• Please add tests to validate your changes, and lint your code using tox -e linters.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community