[core-language][Java][refactor] Task and actor creation options expose public fields breaking encapsulation

[codope]

All the options classes here,BaseTaskOptions, ActorCreationOptions, CallOptions, etc deviate from the standard practice. They follow the builder pattern properly, but we could:

• Make fields final & private; expose getters only.
• Wrap resource map in Collections.unmodifiableMap or Collections.unmodifiableList in constructor to ensure immutability.

This issue just tracks cleaning up the code. Public access is not necessary for interaction with C++ workers via JNI.