NightHawk Explorer support

[idky137]

Zaino needs to serve the following JsonRPC services to support NightHawk block explorer:

• getaddressdeltas: Implement getaddressdeltas #321
• getbestblockhash: 1.2: Add Zcash RPC getbestblockhash #198
• getblockcount: 1.3: Add Zcash RPC getblockcount #199
• getblockhashes (Lower priority?): 1.6: Add Zcash RPC getblockhashes #202
• getblockheader: feat(rpc): add getblockheader endpoint #603
• getdifficulty: 1.9: Add Zcash RPC getdifficulty #205
• getmempoolinfo: 1.10: Add Zcash RPC getmempoolinfo #206
• gettxoutsetinfo: feat(rpc): add gettxoutsetinfo endpoint #595
• getmemoryinfo (Lower priority?): 1.16: Add Zcash RPC getmemoryinfo #212
• getblocksubsidy: feat(rpc): add getblocksubsidy endpoint #592
• getmininginfo: feat(rpc): add getmininginfo endpoint #585
• getnetworksolps: [#214] Add Zcash RPC getnetworksolps passthrough RPC method #573
• getnetworkinfo (Lower priority?): 1.19: Add Zcash RPC getnetworkinfo #215
• getpeerinfo (Low priority): feat(rpc): add getpeerinfo endpoint #587
• validateaddress (Low priority): 1.22: Add Zcash RPC validateaddress #218
• z_validateaddress (Low priority): 1.23: Add Zcash RPC z_validateaddress #219

For each of these RPCs we will need to add / implement the following:

• Define input / output structs.
• Add method definition to ZcashIndexer and implement for FetchService and StateService.
• Add RPC to JsonRPC server.

[ala-mode]

I am commenting in ghcli autotriggering helix editor.. preparing to self-assign.

[ala-mode]

Relevant link from Zebra: ZcashFoundation/zebra#8435 (comment)