Fail SEND_MESSAGE ops if stream is closed for writes

[yashykt]

Fixes #14812
Fail SEND_MESSAGE ops if stream is closed for writes.

Earlier, gRPC Core would not fail SEND_MESSAGE ops if the client had already received a status.

Looks like this was done so as to avoid status being overwritten by the error 'Attempt to send message after stream was closed'. This would happen because the surface layer (call.cc) initiates a CANCEL op when any op fails.

In the case of a streaming call, the C++ API depends on Write calls returning false when the stream is closed. If gRPC Core fails this write and cancels the call, we would lose the status reported by the server too.

This approach creates a bug where Writes on streaming calls never fail even if the stream has been closed.

New Approach -
If gRPC Core gets a SEND_MESSAGE op when the stream is closed for writes, we fail the write but we do not cancel the call.

[yashykt]

cc @a11r

[yashykt]

Issues: #19819, #19422, #19170

[yashykt]

Thanks for reviewing!