[core] Use ActorState_Name to print ActorState

[kevin85421]

Why are these changes needed?

ray/src/ray/protobuf/gcs.proto

Lines 78 to 90 in 8c2d945

	enum ActorState {
	// Actor info is registered in GCS. But its dependencies are not ready.
	DEPENDENCIES_UNREADY = 0;
	// Actor local dependencies are ready. This actor is being created.
	PENDING_CREATION = 1;
	// Actor is alive.
	ALIVE = 2;
	// Actor is dead, now being restarted.
	// After reconstruction finishes, the state will become alive again.
	RESTARTING = 3;
	// Actor is already dead and won't be restarted.
	DEAD = 4;
	}

ActorState is an enum defined in Protobuf. If ActorState_Name is not called, an integer will be printed instead. For example, rpc::ActorTableData::DEAD would print as 4.

• Without this PR: "with status 4"
  

• With this PR: "with status DEAD"
  

I also considered implementing std::ostream &operator<<(std::ostream &out, ...). However, there are several issues:

• ActorState can be printed directly without causing compilation errors, making it difficult to determine whether the overloaded operator is being called.
• A file that references ActorState does not necessarily #include the utility function operator<<.

Related issue number

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    method in Tune, I've added it in doc/source/tune/api/ under the
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