Resolve "RPC: Execute Program"

MERGE REQUEST

Overview

This MR adds the RPCExecuteProgram RPC and a simple integration test. To get it working it also touches a lot of other code. e.g. it hooks up the RPC handlers in network.go to the SiaMux listener.

Example for Visual Changes (ie Screenshot, asciinema)

Checklist

Review and complete the checklist to ensure that the MR is complete before assigned to an approver.

• All new methods or updated methods have clear docstrings
• Testing added or updated for new methods
• Any new packages are added to Makefile and .gitlab-ci.yml
• API documentation updated for API updates
• Module README.md updated for changes to workflow
• Issue added to Sia-UI repo for new supporting features
• Changelog File Created

Issues Closed

Closes

Closes #3864 (closed)