Remove Thread Check for Prefork/Postpork

[chjasonwu]

Is your feature request related to a problem? Please describe.

I'm integrating Puma with gRPC and have encountered a thread consistency validation that occurs during prefork and postfork phases. I'm trying to understand the rationale behind this validation. I conducted load testing without this validation, and the application seemed to perform well.

This relates to the discussion in this thread: #8798 (comment).

Describe the solution you'd like

If removing this validation does not pose an operational risk, I propose eliminating it to ensure compatibility with Puma.

Describe alternatives you've considered

Another approach would be to ensure that Puma forks using the same thread to satisfy the validation. However, the necessity of this thread check for fork safety is unclear to me.

Additional context

n/a

[chjasonwu]

cc @ytaben