* Analyze nullability in script initializer

* C# 8 for scripts for now

* nullable context script test

* extra null check

* added possibility to set c# Language Version on ScriptOptions

* adjust tests

* added ScriptOptionsTests for C# lang version

* adapted tests after rebase

* code review changes

* fixed test names & resx CDATA

* changed the ScriptOptions.WithLanguageVersion error message text and moved it to ScriptingResources.resx

* Update CSharpScriptingResources.Designer.cs

* Revert "Revert "Interactive projects refactoring (#29069)""

This reverts commit e0a8124f.

* Fix bad merge

This reverts commit 41fb51d2.

Remove Repl projects

Remove Microsoft.VisualStudio.InteractiveServices project

Remove Microsoft.CodeAnalysis.InteractiveEditorFeatures

Rename InteractiveEditorFeatures to EditorFeatures.Wpf

Remove empty resource files

Reduce InteractiveFeatures dependencies

Merge InteractiveComponents content into Roslyn.VisualStudio.Setup VSIX

Rename InteractiveFeatures to InteractiveHost

Hook fatal error handlers

Workaround warning CS1574

Exclude CreateTemplateManifestsCacheFile

Do not include satellite assemblies in DesktopHost directory

Remove VB interactive menu item

Delete VisualBasic.EditorFeatures.Wpf

Delete more unused VB interactive code

Fixes #7588

...and update namespaces contained therein accordingly.

...and update namespaces contained therein accordingly.

Previously the command line tests were looking in various directories for csc.exe/vbc.exe. Instead, add a reference to csc/vbc project to the command line unit test assembly, so that we always test what we build and not depend on directories outside of Roslyn.
To make it easy to test the default .rsp file this change links it into the command line unit test project and includes it to resources. The tests then extract the .rsp from the resources and save it to a temp file for testing.
 (changeset 1285693)

Splits Microsoft.CodeAnalysis, Microsoft.CodeAnalysis.CSharp and Microsoft.CodeAnalysis.VisualBasic into portable and desktop assemblies.

Existing Core\Source, CSharp\Source and VisualBasic\Source directories are renamed to Core\Portable, CSharp\Portable and VisualBasic\Portable.
New sibling Desktop folders are added and non-portable source is moved there.
"System.Runtime" references has to be removed in order for the portable project system magic to automatically add facade references.
 (changeset 1281686)