Change fog-ingest to support getting ledger data from a remote mobilecoind

[eranrund]

Motivation

This PR is a followup to #3701. It changes fog-ingest-server to use the BlockProvider trait and support either getting block data from local lmdb files, or from a remote mobilecoind instance. Doing this will allow us to slightly reduce our Azure storage cost.

To verify the performance of this I deployed this branch twice, once without the helm changes and once with it and ran the fog-test-client. I observed the prometheus metrics, and here's what I saw.

Local ledger:

fog_test_client_tx_received_time_bucket{le="1"} 0
fog_test_client_tx_received_time_bucket{le="2"} 0
fog_test_client_tx_received_time_bucket{le="2.5"} 26
fog_test_client_tx_received_time_bucket{le="3"} 27
fog_test_client_tx_received_time_bucket{le="3.5"} 34
fog_test_client_tx_received_time_bucket{le="4"} 46
fog_test_client_tx_received_time_bucket{le="4.5"} 49
fog_test_client_tx_received_time_bucket{le="5"} 49
fog_test_client_tx_received_time_bucket{le="5.5"} 49
fog_test_client_tx_received_time_bucket{le="6"} 49
fog_test_client_tx_received_time_bucket{le="6.5"} 49
fog_test_client_tx_received_time_bucket{le="7"} 49
fog_test_client_tx_received_time_bucket{le="7.5"} 49
fog_test_client_tx_received_time_bucket{le="8"} 49
fog_test_client_tx_received_time_bucket{le="9"} 49
fog_test_client_tx_received_time_bucket{le="10"} 49
fog_test_client_tx_received_time_bucket{le="12"} 49
fog_test_client_tx_received_time_bucket{le="14"} 50
fog_test_client_tx_received_time_bucket{le="16"} 50
fog_test_client_tx_received_time_bucket{le="18"} 50
fog_test_client_tx_received_time_bucket{le="20"} 50
fog_test_client_tx_received_time_bucket{le="+Inf"} 50

Remote ledger:

fog_test_client_tx_received_time_bucket{le="1"} 0
fog_test_client_tx_received_time_bucket{le="2"} 0
fog_test_client_tx_received_time_bucket{le="2.5"} 23
fog_test_client_tx_received_time_bucket{le="3"} 23
fog_test_client_tx_received_time_bucket{le="3.5"} 31
fog_test_client_tx_received_time_bucket{le="4"} 49
fog_test_client_tx_received_time_bucket{le="4.5"} 49
fog_test_client_tx_received_time_bucket{le="5"} 49
fog_test_client_tx_received_time_bucket{le="5.5"} 49
fog_test_client_tx_received_time_bucket{le="6"} 49
fog_test_client_tx_received_time_bucket{le="6.5"} 49
fog_test_client_tx_received_time_bucket{le="7"} 49
fog_test_client_tx_received_time_bucket{le="7.5"} 49
fog_test_client_tx_received_time_bucket{le="8"} 49
fog_test_client_tx_received_time_bucket{le="9"} 49
fog_test_client_tx_received_time_bucket{le="10"} 49
fog_test_client_tx_received_time_bucket{le="12"} 49
fog_test_client_tx_received_time_bucket{le="14"} 49
fog_test_client_tx_received_time_bucket{le="16"} 49
fog_test_client_tx_received_time_bucket{le="18"} 49
fog_test_client_tx_received_time_bucket{le="20"} 49
fog_test_client_tx_received_time_bucket{le="+inf"} 49

The numbers appear very similar, so I think it is okay to move forward with this.