Support producing xcframework that wraps static framework instead of static library

Many 3rd party dependencies in the iOS ecosystem expect to be consumed as a framework and therefore setup their `#import`s in a way that expects that. Today if you build a static xcframework with rules_apple you get a xcframework that wraps a static library. I think we should also support this case to support the include syntax that most projects use, without having to modify the imports to make things work.

The issue names no source files, tests, or entry points. Start by locating the existing rules_apple logic that produces static xcframeworks, then compare its static-library output with the requested static-framework wrapping; done means the rule can produce the requested xcframework while preserving expected iOS import syntax.

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