fix: migrate code base to compiler-cli@6
fix: migrate code base to compiler-cli@6

Temporarily, use deep imports for some internal APIs. Type definitions of compiler-cli are missing an "@internal" class. Long term, we should better switch to the ngtools2_api

See: https://github.com/angular/angular/issues/23112

dherges/ng-packagr,dherges/ng-packagr,dherges/ng-packagr,dherges/ng-packagr