feat(compiler): allow ngIf to use the ngIf expression directly as a guard

Allows a directive to use the expression passed directly to a property
as a guard instead of filtering the type through a type expression.

This more accurately matches the intent of the ngIf usage of its template
enabling better type inference.

Moved NgIf to using this type of guard instead of a function guard.

Closes: #20967

packages/common/src/directives/ng_if.ts

@@ -152,7 +152,8 @@ export class NgIf {
     }
   }
 
-  public static ngIfTypeGuard: <T>(v: T|null|undefined|false) => v is T;
+  /** @internal */
+  public static ngIfUseIfTypeGuard: void;
 }
 
 /**