feat(ivy): first steps towards JIT compilation (#23833)

This commit adds a mechanism by which the @angular/core annotations
for @Component, @Injectable, and @NgModule become decorators which,
when executed at runtime, trigger just-in-time compilation of their
associated types. The activation of these decorators is configured
by the ivy_switch mechanism, ensuring that the Ivy JIT engine does
not get included in Angular bundles unless specifically requested.

PR Close #23833

packages/core/src/ivy_switch.ts

@@ -32,3 +32,5 @@
  *    symbol in `./ivy_switch_false` and `./ivy_switch_false` depending on the compilation mode.
  */
 export * from './ivy_switch_false';
+
+// TODO(alxhub): debug why metadata doesn't properly propagate through this file.