feat(core): properly support inheritance

## Inheritance Semantics:

Decorators:
1) list the decorators of the class and its parents in the ancestor first order
2) only use the last decorator of each kind (e.g. @Component / ...)

Constructor parameters:
If a class inherits from a parent class and does not declare
a constructor, it inherits the parent class constructor,
and with it the parameter metadata of that parent class.

Lifecycle hooks:
Follow the normal class inheritance model,
i.e. lifecycle hooks of parent classes will be called
even if the method is not overwritten in the child class.

## Example

E.g. the following is a valid use of inheritance and it will
also inherit all metadata:

```
@Directive({selector: 'someDir'})
class ParentDirective {
  constructor(someDep: SomeDep) {}

  ngOnInit() {}
}

class ChildDirective extends ParentDirective {}
```

Closes #11606
Closes #12892

tools/@angular/tsc-wrapped/src/schema.ts

@@ -36,6 +36,7 @@ export interface ModuleExportMetadata {
 
 export interface ClassMetadata {
   __symbolic: 'class';
+  extends?: MetadataSymbolicExpression|MetadataError;
   decorators?: (MetadataSymbolicExpression|MetadataError)[];
   members?: MetadataMap;
   statics?: {[name: string]: MetadataValue | FunctionMetadata};