Revert "core: Delayed deserialization for unary/server-streaming calls (#13004)

[kannanjgithub]

This reverts commit 8ba4b48 because this change breaks grpc-kotlin tests that use InProcessTransport by causing a deadlock because ServerCalls.kt only requests the next message after onMessage delivers the current one, and messages get queued because the client hasn't called halfClose yet. When the client halfCloses, InProcessTransport.halfClose defers delivering halfClose if the server's receive queue is non-empty.

Resulting Deadlock:

• ServerCallImpl waits for halfClosed() before dispatching Message 1.
• InProcessTransport waits for call.request(1) before dispatching halfClosed().
• The server waits for Message 1 before calling call.request(1).
• The test hangs indefinitely waiting for closeStatus.await() until the 10s test timeout expires.

There are a few other failures too but those can be fixed in the test code alone.

Internal Test failures: http://shortn/_If0NinnwQ4