Create alternative GRPC validator endpoint for python

[wellingsworth]

Hello,

1. The python client implementation uses a GRPC validator client.
2. The default testnet GRPC endpoint is https://dydx-testnet-archive.allthatnode.com (link). Currently, if I run the following query (via HTTP), I get that this RPC is 11 hours behind.

curl -X GET \
    -H "accept: application/json" \
    "https://dydx-testnet-archive.allthatnode.com/block" \
    | python3 -m json.tool

3. Alternatively, we could use https:/test-dydx.kingnodes.com in the above curl command, but we can't use it as a GRPC validator, since it doesn't open up a GRPC port.

curl -X GET \
    -H "accept: application/json" \
    "https://test-dydx.kingnodes.com/block" \
    | python3 -m json.tool

I request that this repository maintain a list of viable testnet validator GRPCs, OR that it modify the python client to broadcast via HTTP rather than GRPC.