[Heartbeat Logging] Update FirebaseCore dependents for heartbeat logging changes (#9436)

* Set swift_version to 5.3 for core dependents

* Fix Firestore Cmake build

* s/Cmake/CMake

FirebaseFunctions.podspec

@@ -31,6 +31,8 @@ Cloud Functions for Firebase.
   s.cocoapods_version = '>= 1.4.0'
   s.prefix_header_file = false
 
+  s.swift_version = '5.3'
+
   s.source_files = [
     'FirebaseFunctions/Sources/**/*.swift',
   ]