[Generator] Fix missing `$(inherited)` in xcconfig build settings

- Add missing `$(inherited)` values for the build settings `LIBRARY_SEARCH_PATHS` and `HEADER_SEARCH_PATHS` in generated xcconfig files.
- Update tests to explicitly check for these `$(inherited)` values.

Fixes #3908

The `HEADER_SEARCH_PATHS` will no longer be constructed recursively.

Embed frameworks into app and watch extensions.

[Validator] Add private mode

[TargetIntegrator] Remove embed frameworks build phase where not needed

Create an own method #remove_embed_frameworks_script_phase which takes a native target and returns whether modification were made.

Fix watchOS Example Podfile referencing non-existent branch

[Validator] Print the name of the attribute that has the result

[CONTRIBUTING] Minor improvements

Fixes #3546

Collapse public and private pod xcconfig into one

Fixes #3906.

[Copy] Framework support is out of beta

Changed the default template Podspec description to be a comment.

[Installer] Add support for source provider plugin hook