[FEATURE]: Support Python 3.15

[miketheman]

Describe the goal of the feature

(tracking issue)

Python 3.15 alphas are out now, with the first beta scheduled for early May 2026. See https://peps.python.org/pep-0790/ for the full schedule.

Now that ddtrace will fail installation on Python 3.15, it would be good to add testing earlier in the pipeline so that ddtrace will be prepared for 3.15 when it launches around October 2026.

Is your feature request related to a problem?

No response

Describe alternatives you've considered

No response

Additional context

No response

[taegyunkim]

Thanks for reporting. I can't promise a date, but we hope to react to upstream changes sooner than how we did before.