chore: Create plugin iOS native code generation snapshot tests

[mahmoud-elmorabea]

This PR adds unit tests for the native code generated by our Expo plugin.

This PR focuses on the iOS generated code.

Options considered

Option 1: Use Jest's snapshot testing (Recommended)

• This option uses Jest's snapshot testing to capture a snapshot of the result of the generated code by our Expo plugin
• Then for all subsequent runs we use the captured snapshot to make sure that the generated code is still as expected

Option 2: Custom testing

• This option would depend on us writing tests that find certain code parts or lines that are generated
• This option is a bit problematic since we have to handle different versions of Expo by ourselves
• This option is also challenging since we'll probably have to write code that is equality complicated to the code that generate the code under test

[Shahroz16]

Same as other PR, we will be discussing the changes sync. Adding comment because didn't want to leave PRs unattended.