build: move SentryObjCBridge to Sentry target

Move SentryObjCBridge.swift from SentryObjC target to Sentry target
to avoid module conflicts. When Swift code was in SentryObjC, it
could see both the SentryObjC module and Sentry module definitions
of the same types (SentryUser, SentryOptions, etc.), causing
compilation errors.

Architecture is now:
- Sentry.framework: SDK + SentrySDKInternal + SentryObjCBridge
- SentryObjC.framework: pure ObjC with forward declarations

At link time, SentryObjC calls resolve to implementations in Sentry.

Also:
- Fix bridge imports (can't import Sentry when inside Sentry module)
- Add SentryObjC.xcframework to gitignore
- Update Ruby script to not include bridge in SentryObjC target

Author: philprime

.gitignore

@@ -111,6 +111,7 @@ Sentry-Dynamic-WithARM64e.xcframework*
 SentrySwiftUI.xcframework*
 Sentry-WithoutUIKitOrAppKit.xcframework*
 Sentry-WithoutUIKitOrAppKit-WithARM64e.xcframework*
+SentryObjC.xcframework*
 
 current_package_diff.patch