Modernize and Update to .Net 6 and Controllers

[ChadFanguy-usgs]

• Figure out how to use appsettings.json or use another method for saving configuration settings
• Migrate code from Handlers to Controllers (urls will slightly change)

Work has started in UpdateAndDependabot branch:

• https://github.com/USGS-WiM/StreamStatsServices/tree/UpdateAndDependabot

[ChadFanguy-usgs]

Closing this since we plan to switch to a python rewrite. Let's keep the UpdateAndDependabot branch in case we need to reference it later