GH-552: Eliminate extra block increment

[masqrauder]

Follow-up to the original GH-552 with a new branch of the same name.

• With these changes the block number is no longer double-incremented.
• These changes also include additional tests to verify the block number handles the max_block_count size chunks and doesn't skip any blocks by incrementing one too many times.

[bertllll]

This, the use of this TestServer isn't an issue immediately. However, when Syther and Utkarsh completes their work on GH-744, there might not be this thing anymore in the codebase. I've acquired an impression that they go with its alternative only, the MockBlockchainClientServer.

This might surprise you unpleasantly, therefore I'm preparing you for that eventuality. At least after this you could possibly recall I've mentioned it once and it'll bring you there to what you need.