Add `os.pidfd_getfd(pidfd, targetfd, flags=0)` syscall

[maurycy]

Feature or enhancement

Proposal:

os.pidfd_open and signal.pidfd_send_signal are here; os.pidfd_getfd is missing.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/pidfd-getfd-syscall/107203/

https://discuss.python.org/t/add-pidfd-getfd-syscall-to-os-module/19789

Linked PRs

• os.pidfd_getfd(pidfd, targetfd, flags=0) syscall #149465