Delete missing class diagram.
NuGet Updates
Move TestExtensions to SystemTestServices
Make GeometricTestBase setup method virtual.

This also consolidates the methods marked at [Setup] for
RevitNodeTestBase so we can guarantee the setup order.
Add change to proj file for TestServices move,
Ensure DynamoCorePath is set in SystemTestBase
Cleanup unused references.

After the refactor of system test base, and the movement of
TestExtensions, many test libraries had unused references.
Merge pull request #3229 from DynamoDS/MAGN-5402-Cont

Magn 5402 cont