[proto] Remove redundant RPC GetLastCommittedBlockNumber()

[liran-funaro]

Type of change

• Improvement (improvement to code, performance, etc)

Description

• Remove redundant RPC in the coordinator: GetLastCommittedBlockNumber() - It was already covered by GetNextExpectedBlockNumber()
• Remove unnecessary stream check in GetNextExpectedBlockNumber() - The sidecar verifies this anyway before calling this method
• Align API with VC - Replaced GetLastCommittedBlockNumber() with GetNextExpectedBlockNumber()
• Adjust relevant tests

Related issues

• resolves [proto] Unused RPC in the Coordinator: GetLastCommittedBlockNumber #48

[cendhu]

My suggestion is to use the name GetLastCommittedBlockNumber instead of GetNextExpectedBlockNumber. This also aligns with the existing SetLastCommittedBlockNumber. The caller (i.e., the sidecar) can then derive the next expected block number from the last committed block number.

[liran-funaro]

@cendhu The reason GetLastCommittedBlockNumber() was preferred is that it does not require special care when there are no blocks committed.
But I understand the readability issue you raised.

[cendhu]

@cendhu The reason GetLastCommittedBlockNumber() was preferred is that it does not require special care when there are no blocks committed. But I understand the readability issue you raised.

Yes, when I read, I was thinking that GetNextExpectedBlockNumber is the one that is expected by the coordinator which is one greater than the last received block. Later, I understood it is returning the last committed block + 1. We can rename it to GetNextToBeCommittedBlockNumber or GetNextBlockNumberToCommit and still retain the removal of the extra proto message.

[liran-funaro]

I opted for GetNextBlockNumberToCommit()

[cendhu]

Resolve conflicts. Otherwise, LGTM.