Prepare for Thor upgrade v2.1.5 and v2.1.6

[victhorbi]

Depends on : #1577

• support raw query parameter in the /blocks, we would need to add new parameter (double check) #1602
• add Node Health Endpoint, we could possibly add support for this call #1603
• check if the vechain-sdk-js uses POST /accounts #1604
• check if the vechain-sdk-js uses POST /accounts/{account} #1605
• check if the vechain-sdk-js uses Websocket /subsciptions/beat #1606

[victhorbi]

@leszek-vechain can we close this task? Where can I find the outcome?

[leszek-vechain]

So for each of the subtask, I put a comment in there, but I can summarise it:

1. It seems that, we currently support only expanded and compressed blocks. Need to add raw option with appropriate tests for that. This possibly can affect RPC calls too.
2. New functionality, described here: https://github.com/vechain/thor/blob/master/docs/hosting-a-node.md#admin, we would need to add support for 2 new endpoints, however their availability is decided when node starts, so they are not always on.
3. Does not seem we support this method.
4. Does not seem we support this method.
5. We support both old /beat and new /beat2, we would need to remove it.

I think for point 1/2 we should discuss it a bit more.