[Release Tooling] Add resources, if any, to bundle within xcframework platform slices (approach 1)

[ncooke3]

• This PR should only affect privacy manifests to maintain Xcode 14 compat.
• Test if SPM accepts xcframeworks with embedded resources (since there was that gRPC issue with the bundle at the root of the xcframework). If there's an issue, it may be fixed by signing the xcframework

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[paulb777]

Looks like we need this for 10.21.0 now that GTMSessionFetcher has a privacy manifest.

Anything else needed to be done before merging?

[ncooke3]

Anything else needed to be done before merging?

Yes, the issue with this PR is that it changes the DevX for zip customers still using Xcode 14. As of the latest release, the Firebase.zip has three resources:

./FirebaseInAppMessaging/Resources/InAppMessagingDisplayResources.bundle
./FirebaseFirestore/Resources/gRPCCertificates-Cpp.bundle
./GoogleSignIn/Resources/GoogleSignIn.bundle

These resources are moved inside the xcframework they correspond to, so the integration instructions will be more complex (e.g. "for each of these SDKs that contain non-privacy manifest related resource bundles, copy the resource bundle out of a platform slice and add it to your app".

I have some work locally I did a few weeks back that changes this PR's implementation to do the following:

• Don't change the locations of the existing resource bundles in the zip
• For resource bundles containing privacy manifests, embed them within the XCFramework.

This alternative approach is Xcode 14 friendly.

[paulb777]

Thanks. I believe we can drop the gRPC resource file since Firestore doesn't use it - it gets the contents from code. That would address #9184 and reduce the usability impact of this change.