Add new command line parameters for working with the project:
* `-NoBuild`, `-NoRestore` - these already existed, but users found it hard to discover this powershell syntax: '-build:$false'
* `-Arch`/`--arch` - set the target CPU architecture to build. Defaults to x64
* `--os-name` - on non-Windows builds, manually specify if the build should target Alpine. generic Linux, or MacOS
* Rename flags used to build specific project types. The pattern now is `--build-$(group)` or `--no-build-$(group)` (In PowerShell its `-Build$(Group)` or `-NoBuild$(Group). Example: -NoBuildJava
Changes to build definitions:
* Update the ci build definition to build all supported architectures
* Support publishing multiple artifacts per job
Other changes:
* `-NoBuild` implies `-NoRestore`
* Add new properties, `TargetArchitecture`, `TargetOsName`, and `TargetRuntimeIdentifier`
* Replace usages of `SharedFxRid` with these new properties
* To make `--no-build-nodejs` actually work, replaced Components.Browser.JS.csproj with Components.Browser.JS.npmproj
* Fix errors when building for win-arm on a clean machine
* Fix a few other project errors, like using the wrong syntax for DefaultItemExcludes, or using the wrong Platform value for x86
Update the build scripts to support building subfolders or subgroups of projects
* Add build scripts for ci
* Remove obsolete scripts
* Add flags like --test and --pack to control running just test or packaging
* Add flags like --managed and --native to control building sub-types of projects
* Remove KoreBuild bootstrapper flags
* Update to extensions 3.0.0-preview.18619.1 (needed to get a fix for aspnet/Extensions#815 to make this change work on MSBuild.exe)
Nate McMaster