spm: add .macCatalyst to FirebasePerformance and FirebaseInAppMessaging targets

Under SPM, the Wrap-based targets for FirebasePerformance and
FirebaseInAppMessaging gate their real product dependencies with
`.when(platforms: [.iOS, ...])` that omits `.macCatalyst`. On Mac
Catalyst, SPM therefore only links the `SwiftPM-PlatformExclude/*Wrap`
dummies (`FirebasePerformanceTarget.o` / `FirebaseInAppMessagingTarget.o`)
and never compiles the real modules.

This is speculative / discussion-only: draft PR asking whether the
Catalyst exclusion under SPM was intentional. CocoaPods consumers with
Mac Catalyst apps have historically been able to compile and link these
products via the iOS podspec slice through the `Firebase/Firebase.h`
umbrella, so the current SPM behavior is a divergence from that
historical path.

Package.swift already declares `.macCatalyst(.v15)` in
`Package.platforms` and uses `.macCatalyst` alongside `.iOS` /
`.tvOS` / `.macOS` for many other targets, so this change follows
existing style.

Source-level compile fitness on Catalyst is not verified by this change:
FirebasePerformance's Objective-C sources already special-case
`TARGET_OS_MACCATALYST` for CoreTelephony and FirebaseInAppMessaging's
sources gate on `TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION`
(TARGET_OS_IOS is 1 under Catalyst), but Google CI is the ground truth.

App Distribution is intentionally left iOS-only.

Consumer context: invertase/react-native-firebase#8933

Author: mikehardy

Package.swift

@@ -747,7 +747,8 @@ let package = Package(
     .target(
       name: "FirebaseInAppMessagingTarget",
       dependencies: [
-        .target(name: "FirebaseInAppMessaging", condition: .when(platforms: [.iOS, .tvOS])),
+        .target(name: "FirebaseInAppMessaging",
+                condition: .when(platforms: [.iOS, .tvOS, .macCatalyst])),
       ],
       path: "SwiftPM-PlatformExclude/FirebaseInAppMessagingWrap"
     ),
@@ -883,7 +884,7 @@ let package = Package(
     .target(
       name: "FirebasePerformanceTarget",
       dependencies: [.target(name: "FirebasePerformance",
-                             condition: .when(platforms: [.iOS, .tvOS, .visionOS]))],
+                             condition: .when(platforms: [.iOS, .tvOS, .visionOS, .macCatalyst]))],
       path: "SwiftPM-PlatformExclude/FirebasePerformanceWrap"
     ),
     .target(