Rename instanceName and storageID to serviceName (#11599)

For consistency, renamed both instanceName and storageID to serviceName for consistency.

In all cases, the serviceName is an identifier that differentiates multiple GACAppCheck instances such as when there are multiple FIRApps in use, or multiple dependent SDKs (e.g., Firebase and Google Sign-In). This unique identifier ensures their state is not shared in the Keychain or in User Defaults.

AppCheckCore/Sources/DebugProvider/GACAppCheckDebugProvider.m

@@ -50,10 +50,10 @@ static NSString *const kDebugTokenUserDefaultsKey = @"FIRAAppCheckDebugToken";
   return self;
 }
 
-- (instancetype)initWithStorageID:(NSString *)storageID
-                     resourceName:(NSString *)resourceName
-                           APIKey:(nullable NSString *)APIKey
-                     requestHooks:(nullable NSArray<GACAppCheckAPIRequestHook> *)requestHooks {
+- (instancetype)initWithServiceName:(NSString *)serviceName
+                       resourceName:(NSString *)resourceName
+                             APIKey:(nullable NSString *)APIKey
+                       requestHooks:(nullable NSArray<GACAppCheckAPIRequestHook> *)requestHooks {
   NSURLSession *URLSession = [NSURLSession
       sessionWithConfiguration:[NSURLSessionConfiguration ephemeralSessionConfiguration]];