Remove ProjectJsonMigration and its test from solution file
Change dependecy by package reference instead of project 2 project
Construct the sln and dotnet new with wrapper that is used in migrate
package
Add reference to Nuget ProjectModel etc since CrossGen need it and it
cannot automatically get the reference
* Reduce test target complexity [and running time]
* WiP
* Enable building tests via solution
Remove deprecated tests
Make Microsoft.DotNet.Tools.Tests.Utilities portable-only
Remove MSI tests from the solution as they are the only tests that currently require dekstop.
* Enable building of tests
* Move migration tests to TA to allow them to self-restore
* Reduce project nesting and test directory name
* Fixing argument parsing in add package command
* Adding check to throw if extra args were passed
* Removing string and adding test cases for dotnet add package command
* Add new test to test.sln, and fix naming, and clean csproj
This commit introduces a solution file for test projects and modifies
the needed build targets to restore the test solution instead of each
test project separately.
It also introduces a new template called "sln" to dotnet new that drops
a template solution file for users to consume.
Fixes#5099
