Explicitly handle friend clasess (#55843)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55843

Changelog: [Internal]

Adds explicit support for friend classes in the C++ API snapshot. Doxygen treats friends as variables of type "friend". For the snapshot use case, we cover that special case and store them as explicit `FriendMember`. This allows for correctly ignoring friend definitions when qualifying identifiers.

Reviewed By: cipolleschi

Differential Revision: D94901510

fbshipit-source-id: fd2f8d7798eee2bfb5778a0969cf77d20d9978a7