Fix DoFnInvoker cache collision for generic types (#37355)

This fixes a bug where ByteBuddyDoFnInvokerFactory would return the same cached invoker for different generic instantiations of the same DoFn class.

Changes:
1. Introduced InvokerCacheKey with TypeDescriptors to ensure unique cache entries.
2. Updated generateInvokerClass to append type-based hash suffix.
3. Added regression test (testCacheKeyCollisionProof).

This PR fixes a critical issue where ByteBuddyDoFnInvokerFactory failed to distinguish between different generic instantiations of the same DoFn class (e.g., MyFn<String> vs MyFn<Integer>).

1. Cache Key Strategy: Introduced InvokerCacheKey to include input/output TypeDescriptors in the cache lookup.
2. Class Naming: Updated generateInvokerClass to append a type-based hash suffix to ensure unique class names.
3. Robustness (The Fix): Added defensive try-catch blocks when accessing TypeDescriptors.
   - Some internal transforms (like MapElements) throw IllegalStateException if getOutputTypeDescriptor() is called after serialization.
   - In these cases, the factory now gracefully falls back to using Object.class (legacy behavior), ensuring backward compatibility for transforms that do not retain type information at runtime.