Add RPCs for external RandomX mining

[us77ipis]

Problem

• No external RandomX mining possible.
• Mining multiple algorithms at the same time is currently not possible.
• The algorithm getblocktemplate RPC uses for its blocks depends on the value the user selects for mining in the GUI of the wallet / in the config.

Root Cause

Not implemented yet.

Solution

The solution was to:

1. Add an algo parameter to the getblocktemplate RPC which overrides any mining algorithm specified in the config / GUI.
2. Add a new RPC rxrpcsb for submitting randomx blocks, analogous to pprpcsb. This makes it possible to mine at the same time progpow, randomx and sha256d externally, independently of what you may additionally mine using the wallet.

Bounty PR

?

Bounty Payment Address

sv1qqpjsrc60t60jhaywj5krmwla52ska70twc7wun6qnee65guxhvtxegpqwhuxypra4jn3pq86s24ryltcw6g2ss4573hyqac9u4g23m9mvxpyqqqwny49k

Unit Testing Results

Tested by mining at the same time progpow blocks with t-rex miner and randomx blocks with xmrig, where both found at least one block.

[WetOne]

utACK 9974e541fa1074eec0d43fd75371c4431fb9232d

[us77ipis]

Now you merged it with the commented code still there?

[codeofalltrades]

Yes, I wanted to get it merged. I need to update the copyrights before the release. I will clean this up then if it hasn't been already.