[tests] update schemes for testing

* Change OneSignalUserTests build configs to "Test"
* Add OS_TEST preprocessor macro (Test) to OneSignalOSCore which is needed for the reduced flush interval

Author: nan-li

iOS_SDK/OneSignalSDK/OneSignal.xcodeproj/project.pbxproj

@@ -6524,6 +6524,7 @@
 				DYLIB_CURRENT_VERSION = 1;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_TESTABILITY = YES;
+				GCC_PREPROCESSOR_DEFINITIONS = OS_TEST;
 				GENERATE_INFOPLIST_FILE = YES;
 				INFOPLIST_FILE = OneSignalOSCoreFramework/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 11.0;

iOS_SDK/OneSignalSDK/OneSignal.xcodeproj/xcshareddata/xcschemes/OneSignalUserTests.xcscheme

@@ -7,7 +7,7 @@
       buildImplicitDependencies = "YES">
    </BuildAction>
    <TestAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES"
@@ -27,7 +27,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Test"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"