Update version numbers, guids and readme for M54, 6.5.0
Update version numbers, guids and readme for M54, 6.5.0

PiperOrigin-RevId: 267495896

firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk