VS2019/Rider BETA 3

Stepping back from .Net6.0 to .Net4.8 because VS2019 does not support 6.0.

This is the 3rd BETA: A BETA until I get confirmation that all solutions build on VS2019.

Completed VS.Net/Rider BETA

Why it's a BETA: Needs to be tested on VisualStudio.Net & Windows. (Built with Rider/MacOS)

Update to previous release:
Changed the example used in /GettingItWorking to have actual implementation code and a failing test. So the GettingItWorking lab--like most other labs--has a primary goal and an optional goal. Primary: Make sure the IDE can build and run the tests (this is the very first lab). Secondary: Fix the implementation and watch the tests go from red to green.

Consolidated VS.Net/Rider BETA

Major improvements done with Rider:

1. Hypothetically compatible with both VS.Net and Rider (ergo BETA)
2. TestedTrek has improved Characterization tests and incorporates language improvements for readability.
3. LunEx folder recreated as the much simplified and improved LunExLab

Full Changelog: https://github.com/AgileInstitute/labs-csharp-mstest/commits/v2.0.1-beta