Stop using /v1a/transaction?type=block&count=1 to query the best block

[andreabadesso]

"I don't really like using this API to get the network height but we still don't have an endpoint for that. Maybe we should add one, it's a simple and important API.

In the meantime maybe we could use /v1a/get_block_template, this returns the template of the block to be mined.

response.metadata.height is the block height to be mined, so the network height is this value -1. I still don't like it, so not sure if we should change.

One of the reasons I don't like using this API is because it was developed to be used on the explorer. With the new explorer service, this API might become deprecated."

Originally posted by @pedroferreira1 in #1 (comment)