Spawning a subprocess crashes the interpreter if subinterpreters exist

• uvloop version: 0.21.0
• Python version: 3.13.0
• Platform: Linux
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: yes
• Does uvloop behave differently from vanilla asyncio? How?: vanilla asyncio doesn't crash

MWE:

import asyncio

import _interpreters as interpreters
import uvloop

async def main():
    interp_id = interpreters.create()
    await asyncio.create_subprocess_exec("sleep", "2")
    interpreters.destroy(interp_id)  # this is never reached


asyncio.run(main(), loop_factory=uvloop.new_event_loop)

Crash log:

Fatal Python error: PyThreadState_Get: the function must be called with the GIL held, after Python initialization and before Python finalization, but the GIL is released (the current Python thread state is NULL)
Python runtime state: initialized

Current thread 0x00007fa5713c8740 (most recent call first):
  File "/usr/lib64/python3.13/asyncio/subprocess.py", line 224 in create_subprocess_exec
  File "/home/alex/workspace/anyio/bug-trio.py", line 8 in main
  File "/usr/lib64/python3.13/asyncio/runners.py", line 118 in run
  File "/usr/lib64/python3.13/asyncio/runners.py", line 194 in run
  File "/home/alex/workspace/anyio/bug-trio.py", line 12 in <module>

Extension modules: uvloop.loop (total: 1)

If I destroy the subinterpreter before spawning the subprocess, it works fine.

Start by running the supplied MWE with uvloop 0.21.0 and Python 3.13.0 on Linux, then compare it with vanilla asyncio. Inspect the subprocess path involving uvloop.new_event_loop and uvloop.loop, using asyncio/subprocess.py line 224 and the reported crash as the reproduction and completion criteria.