[RPC] re introducing filtering args in getbalance

[furszy]

Have re introduced the filtering arguments that were removed when the accounts system got deprecated in getbalance. With this, getbalance RPC command will be able, again, to filter by watch-only, minimum depth and include/exclude delegated balance.

[random-zebra]

With the removed argument, need to lower the size in the checks accordingly (see comments inlined).

btw, styling nit: could use a more compact syntax, like

    const int paramsSize = request.params.size();
    const int nMinDepth = (paramsSize > 0 ? request.params[0].get_int() : 0);
    isminefilter filter = ISMINE_SPENDABLE | (paramsSize > 1 && request.params[1].get_bool() ? ISMINE_WATCH_ONLY : ISMINE_NO);
    filter |= (paramsSize <= 2 || request.params[2].get_bool() ? ISMINE_SPENDABLE_DELEGATED : ISMINE_NO);

    return ValueFromAmount(pwalletMain->GetAvailableBalance(filter, true, nMinDepth));

Also, the initial check for the help needs to be updated to

if (request.fHelp || 
    (request.params.size() > 4 && IsDeprecatedRPCEnabled("accounts")) || 
    (request.params.size() > 3 && !IsDeprecatedRPCEnabled("accounts")))

[furszy]

yeah, great review zebra.
Made all of the changes 👍 .
We will need to add some tests for this in the future.

[random-zebra]

Agreed on the need for more specific tests over getbalance RPC.
utACK 35af377