feat(ngUpgrade): add support for AoT compiled upgrade applications

This commit introduces a new API to the ngUpgrade module, which is compatible
with AoT compilation. Primarily, it removes the dependency on reflection
over the Angular 2 metadata by introducing an API where this information
is explicitly defined, in the source code, in a way that is not lost through
AoT compilation.

This commit is a collaboration between @mhevery (who provided the original
design of the API); @gkalpak & @petebacondarwin (who implemented the
API and migrated the specs from the original ngUpgrade tests) and @alexeagle
(who provided input and review).

This commit is an starting point, there is still work to be done:

* add more documentation
* validate the API via internal projects
* align the ngUpgrade compilation of A1 directives closer to the real A1
  compiler
* add more unit tests
* consider support for async `templateUrl` A1 upgraded components

Closes #12239

modules/@angular/upgrade/index.ts

@@ -12,5 +12,5 @@
  * Entry point for all public APIs of the upgrade package.
  */
 export * from './src/upgrade';
-
+export * from './src/aot';
 // This file only reexports content of the `src` folder. Keep it that way.