[iOS] Support Nix iOS dev shell

Summary:
Allow for nix environment to be utilized for iOS native build.

Introduces tooling such as protoc and rustup which are required for
the build to succeed

https://linear.app/comm/issue/ENG-1999

Depends on D5478 D5319

Test Plan:

nix develop .#ios

# if you want to verify from scratch
git clean -xfd
yarn cleaninstall

cd native/ios
pod install

# Actual build may take a while
cd ..
yarn react-native run-ios --simulator='iPhone 14 Pro' --configuration=Release

Reviewers: atul, varun

Reviewed By: atul

Subscribers: ashoat, tomek, abosh

Differential Revision: https://phab.comm.dev/D5479