refactor(core): change module semantics

This contains major changes to the compiler, bootstrap of the platforms
and test environment initialization.

Main part of #10043
Closes #10164

BREAKING CHANGE:
- Semantics and name of `@AppModule` (now `@NgModule`) changed quite a bit.
  This is actually not breaking as `@AppModules` were not part of rc.4.
  We will have detailed docs on `@NgModule` separately.
- `coreLoadAndBootstrap` and `coreBootstrap` can't be used any more (without migration support).
  Use `bootstrapModule` / `bootstrapModuleFactory` instead.
- All Components listed in routes have to be part of the `declarations` of an NgModule.
  Either directly on the bootstrap module / lazy loaded module, or in an NgModule imported by them.

modules/@angular/compiler-cli/integrationtest/src/a/multiple_components.ts

@@ -8,10 +8,7 @@
 
 import {Component} from '@angular/core';
 
-@Component({
-  selector: 'my-comp',
-  template: '<div></div>',
-})
+@Component({selector: 'my-comp', template: '<div></div>', directives: [NextComp]})
 export class MultipleComponentsMyComp {
 }