[core][experimental] Check whether the channel is closed for the shared memory write operation

[kevin85421]

Why are these changes needed?

• In Fix for incorrect channel read behavior after accelerated DAG teardown #46320, a check is added in CoreWorker::Get to avoid a mutable object being considered a normal immutable object after the channel is closed and the reader is unregistered.

• For the channel's write operation, the function CoreWorker::ExperimentalChannelWriteAcquire will only be called by a mutable object, and thus it doesn't have the issue of considering a mutable object as an immutable object.

• If we write to a channel after it is closed, an exception will be thrown as expected. However, the exception is thrown by MutableObjectManager::WriteAcquire, which is asymmetric with the codepath of the read operation. For the read operation, the exception is thrown by CoreWorker::Get instead of MutableObjectManager. Hence, this PR adds a check in CoreWorker::ExperimentalChannelWriteAcquire.
  

  ray/src/ray/core_worker/experimental_mutable_object_manager.cc

  Line 234 in 6a7521c

  RAY_RETURN_NOT_OK(object->header->CheckHasError());

• Remove IsChannelClosed / ReaderChannelRegistered / WriterChannelRegistered because they are unused after this PR.

Related issue number

#46320 (comment)

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