FirebaseCore directory structure update (#4590)

Author: paulb777

CMakeLists.txt

@@ -245,7 +245,7 @@ find_package(XCTest)
 enable_testing()
 include(compiler_setup)
 
-add_subdirectory(Firebase/Core)
+add_subdirectory(FirebaseCore)
 add_subdirectory(Firestore)
 add_subdirectory(GoogleUtilities)
 add_subdirectory(Interop/Auth)

Dangerfile

@@ -71,7 +71,7 @@ has_license_changes = didModify(["LICENSE"])
 @has_abtesting_changes = hasChangesIn("FirebaseABTesting/")
 @has_auth_changes = hasChangesIn("Firebase/Auth")
 @has_core_changes = hasChangesIn([
-  "Firebase/Core/",
+  "FirebaseCore/",
   "Firebase/CoreDiagnostics/",
   "CoreOnly/"])
 @has_database_changes = hasChangesIn("Firebase/Database/")