Decide hybrid SDK API marker for v9 #6039

As we mark more SDK surface @ApiStatus.Internal ahead of v9 package moves, some types/methods are still consumed by hybrid SDKs (Flutter, React Native, etc.) even when they are not customer-facing.

@ApiStatus.Internal alone does not distinguish hybrid-facing surface from pure SDK plumbing, so hybrid consumers can be broken by a later relocate/remove pass.

Known examples called out during review of the utils Internal pass:

• io.sentry.util.LoadClass
• io.sentry.util.TracingUtils

Context: NoOp stubs and most util helpers were recently marked Internal (#6016, #6017); hybrids were explicitly left unmarked for now.

Action taken on behalf of Nelson Osacky.