Drop support for Net 2.0 and Net 3.0 frameworks versions

[dupdob]

I propose to drop support for Net framework versions 2.0 and 3.0. This would allow to clean up the code, reduce the size of the solution, reduce build time, simplify some of the checks and many other benefits
Net framework versions 2.0 and 3.0 has been obsolete for quite some time now and are no longer support by NUnit.
Ending support for Net 2.0 and 3.0 impact will be that newer versions (> V2.51 at the time of writing) can no longer be used with those framework versions. Compatible versions (2.0 <-> 2.5) remain available on nuget.

if you require continuous support for those frameworks, please describe on which projects and why.

Expected Behavior

No Net 2.0 and Net 3.0 assemblies in the package.

Current Behavior

Net 2.0 and Net 3.0 assemblies are in the package.

Possible Solution

Remove assemblies from package and remove old version specific code in source files.

Code that reproduce the issue

NA

Context

NA

Your Environment

NA