[native] [1/34] ReactNav6: Drop "dangerously" from getParent and getState

Summary:
Context on change here.

Depends on D5393

Test Plan: Flow + ran the app on my phone and played around with it

Reviewers: atul, tomek, bartek

Reviewed By: atul

Subscribers: abosh

Differential Revision: https://phab.comm.dev/D5394