Merge #18594: cli: display multiwallet balances in -getinfo

5edad5ce5d test: add -getinfo multiwallet functional tests (Jon Atack)
903b6c117f rpc: drop unused JSONRPCProcessBatchReply size arg, refactor (Jon Atack)
afce85eb99 cli: use GetWalletBalances() functionality for -getinfo (Jon Atack)
9f01849a49 cli: create GetWalletBalances() to fetch multiwallet balances (Jon Atack)
743077544b cli: lift -rpcwallet logic up to CommandLineRPC() (Jon Atack)
29f2cbdeb7 cli: extract connection exception handler, -rpcwait logic (Jon Atack)

Pull request description:

  This PR is a client-side version of #18453, per review feedback there and [review club discussions](https://bitcoincore.reviews/18453#meeting-log). It updates `bitcoin-cli -getinfo` on the client side to display wallet name and balance for the loaded wallets when more than one is loaded (e.g. you are in "multiwallet mode") and `-rpcwallet=` is not passed; otherwise, behavior is unchanged.

  before
  ```json
  $ bitcoin-cli -getinfo -regtest
  {
    "version": 199900,
    "blocks": 15599,
    "headers": 15599,
    "verificationprogress": 1,
    "timeoffset": 0,
    "connections": 0,
    "proxy": "",
    "difficulty": 4.656542373906925e-10,
    "chain": "regtest",
    "balance": 0.00001000,
    "relayfee": 0.00001000
  }

  ```
  after
  ```json
  $ bitcoin-cli -getinfo -regtest
  {
    "version": 199900,
    "blocks": 15599,
    "headers": 15599,
    "verificationprogress": 1,
    "timeoffset": 0,
    "connections": 0,
    "proxy": "",
    "difficulty": 4.656542373906925e-10,
    "chain": "regtest",
    "balances": {
      "": 0.00001000,
      "Encrypted": 0.00003500,
      "day-to-day": 0.00000120,
      "side project": 0.00000094
    }
  }
  ```
  -----

  `Review club` discussion about this PR is here: https://bitcoincore.reviews/18453

  This PR can be manually tested by building, creating/loading/unloading several wallets with `bitcoin-cli createwallet/loadwallet/unloadwallet` and running `bitcoin-cli -getinfo` and `bitcoin-cli -rpcwallet=<wallet-name> -getinfo`.

  `wallet_multiwallet.py --usecli` provides regression test coverage on this change, along with `interface_bitcoin_cli.py` where this PR adds test coverage.

  Credit to Wladimir J. van der Laan for the idea in https://github.com/bitcoin/bitcoin/issues/17314 and https://github.com/bitcoin/bitcoin/pull/18453#issuecomment-605431806.

ACKs for top commit:
  promag:
    Tested ACK 5edad5ce5d.
  jnewbery:
    utACK 5edad5ce5d
  meshcollider:
    Code review ACK 5edad5ce5d

Tree-SHA512: 4ca36c5f6c49936b40afb605c44459c1d5b80b5bd84df634007ca276b3f6c102a0cb382f9d528370363ee32c94b0d7ffa15184578eaf8de74179e566c5c5cee5

src/rpc/request.h

@@ -26,7 +26,7 @@ bool GetAuthCookie(std::string *cookie_out);
 /** Delete RPC authentication cookie from disk */
 void DeleteAuthCookie();
 /** Parse JSON-RPC batch reply into a vector */
-std::vector<UniValue> JSONRPCProcessBatchReply(const UniValue &in, size_t num);
+std::vector<UniValue> JSONRPCProcessBatchReply(const UniValue& in);
 
 class JSONRPCRequest
 {