* nit: Remove useless `$(HasReferenceAssembly)` settings
- set in /Directory.Build.targets
- `true` only in `$(IsAspNetCoreApp)` projects
* nit: Remove useless `$(CompileUsingReferenceAssemblies)` settings
- no current versioning differences between ref/ and src/ assemblies when targeting default TFM
* Add more `$(GenerateDocumentationFile)` settings
- increases the number of generated doc files, mostly without problems
- !fixup! correct typo in `DebugProxyHost` doc comments
- was not generating a doc file before
- remove previous (ineffective) src/Components/Directory.Build.targets setting
- nit: remove a duplicate `$(GenerateDocumentationFile)` setting
* nit: Remove useless `$(IsPackable)` settings
- only analyzers and implementation projects are packable by default
- main use case for explicit setting is projects shipping only in shared framework
- conditional setting in src/Mvc/Directory.Build.props just subset logic in /Directory.Build.targets
* nit: Remove useless `$(IsProjectReferenceProvider)` settings
- only implementation projects are providers by default
* nit: Remove useless `$(IsTestAssetProject)` settings
- set in src/Mvc/test/WebSites/Directory.Build.props
* !fixup! Looks like `InProcessNewShimWebSite` must compile w/o ref/ assemblies
- restore `$(CompileUsingReferenceAssemblies)` in this one project
c4c6e25a06