Cleanup cake file, add targets, fix for iOS Pair (#7241)

* Cleanup cake file, add targets, fix for iOS Pair

* - fix sln argument

* - add dogfood ps1

* - pack maui before opening external sln

* - add "pack" argument

* - exit earlier

* - script cleanup

* - move dogfood into cake and condtionally run

* - fix pack checks

* - open VS even if build tasks fail to build

* - change to warning

* - change CI check to error

* - set dotnet_root

* - fix vsmac

* - changes to omnisharp

* - switch to flags

* - fix clean