change hosttree map to fingerprint

MERGE REQUEST

MR Guidelines

Overview

This MR adds a fingerprint to SiaPublicKeys and makes use of that in the host tree to allow for a followup that let's us query hosts by a shorter fingerprint.

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