WIP: feat: add pubkeyToPkh and addrToPkh to keyUtils

[coolaj86]

Overview

We have a few conflicting concerns:

• we want devs to be able to interop with other cryptocurrency libraries
• we don't want hard dependencies on our own where there's a clear separation of concerns
• providing in-code, no-dep defaults causes some sites and bundlers, like bundlephobia, to fail
• getaddressutxos is unreliable
  getaddressdeltas and getaddressmempool are missing script dashpay/dash#6215
• getaddressdeltas and getaddressmempool are reliable, but are missing script
getaddressdeltas and getaddressmempool are missing script dashpay/dash#6215

To solve this we can do any of:

• leave more tedium to the developer (current)
• add new convenience methods to keyUtils (proposed)
• create a hard dependency on DashKeys (reasonable, but not prefered)

The Cumbersome Code

In particular, going from the tx draft to the tx final + signed requires a bit more ceremony than I'd like:

        let draftTx = dashTx.legacy.draftSingleOutput({ utxos, inputs, output });
        console.log('DEBUG draftTx', draftTx);

        // See https://github.com/dashhive/DashTx.js/pull/77
        for (let input of draftTx.inputs) {
            let addressInfo = keysMap[input.address];
            Object.assign(input, {
                publicKey: addressInfo.publicKey,
                pubKeyHash: addressInfo.pubKeyHash,
            });
        }
        for (let output of draftTx.outputs) {
            if (output.pubKeyHash) {
                continue;
            }
            if (!output.address) {
                throw new Error(`output is missing 'address' and 'pubKeyHash'`);
            }
            let pkhBytes = await DashKeys.addrToPkh(output.address, {
                version: 'mainnet',
            });
            Object.assign(output, {
                pubKeyHash: DashKeys.utils.bytesToHex(pkhBytes),
            });
        }

        draftTx.inputs.sort(DashTx.sortInputs);
        draftTx.outputs.sort(DashTx.sortOutputs);