refactor(ivy): move directive into elementStart (#21374)

We used to have a separate `directive` instruction for instantiating
directives. However, such an instruction requires that directives
are created in the correct order, which would require that template
compiler would have knowledge of all dependent directives. This
would break template compilation locality principle.

This change only changes the APIs to expected form but does
not change the semantics. The semantics will need to be corrected
in subsequent commits. The semantic change needed is to
resolve the directive instantiation error at runtime based on
injection dependencies.

PR Close #21374

packages/core/src/render3/interfaces/definition.ts

@@ -57,6 +57,11 @@ export interface DirectiveDef<T> {
    */
   methods: {[P in keyof T]: P};
 
+  /**
+   * Name under which the directive is exported (for use with local references in template)
+   */
+  exportAs: string|null;
+
   /**
    * factory function used to create a new directive instance.
    *
@@ -131,6 +136,7 @@ export interface DirectiveDefArgs<T> {
   outputs?: {[P in keyof T]?: string};
   methods?: {[P in keyof T]?: string};
   features?: DirectiveDefFeature[];
+  exportAs?: string;
 }
 
 export interface ComponentDefArgs<T> extends DirectiveDefArgs<T> {