* 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
* WIP support solution folders for dotnet add and remove
* Add/remove solution folders based on directory hierarchy
* Fix tests
* Disable the solution building tests
* Address PR comments
* Fix a build break due to a new tool version used in the build
* Create SlnProjectExtensions and SlnProjectCollectionExtensions per PR comments
* WIP Improve sln migration tests
* Simple migration test
* Improve the test
* WIP update test assets
* Update test
* Test a bug fix
* Add another migrate sln test
* Fix FilePath related tests
* Finish the migrate sln tests
* Fix tests
* Fix another path issue