feat(common): rename underlying NgFor class and add a type parameter (#14104)

Note, this affects the underlying class and should not affect usage.

DEPRECATION:
- the `NgFor` class is now deprecated. Use `NgForOf<T>` instead.
  IMPORTANT: Only the `NgFor` class is deprecated, not the `ngFor`
  directive. The `*ngFor` and related directives are unaffected by
  this change  as references to the `NgFor` class generated from
  templates will be automatically converted to references to
  `NgForOf<T>` without requiring any template modifications.
- `TrackByFn` is now deprecated. Use `TrackByFunction<T>` instead.

Migration:
- Replace direct references to the `NgFor` class to `NgForOf<any>`.
- Replace references to `TrackByFn` to `TrackByFunction<any>`.

BREAKING CHANGE:
A definition of `Iterable<T>` is now required to correctly compile
Angular applications. Support for `Iterable<T>` is not required at
runtime but a type definition `Iterable<T>` must be available.

`NgFor`, and now `NgForOf<T>`, already supports `Iterable<T>` at
runtime. With this change the type definition is updated to reflect
this support.

Migration:
- add "es2015.iterable.ts" to your tsconfig.json "libs" fields.

Part of #12398

PR Close #14104

modules/@angular/language-service/src/expressions.ts

@@ -728,7 +728,8 @@ function getVarDeclarations(info: TemplateInfo, path: TemplateAstPath): SymbolDe
           const value = context.get(variable.value);
           if (value) {
             type = value.type;
-            if (info.template.query.getTypeKind(type) === BuiltinType.Any) {
+            let kind = info.template.query.getTypeKind(type);
+            if (kind === BuiltinType.Any || kind == BuiltinType.Unbound) {
               // The any type is not very useful here. For special cases, such as ngFor, we can do
               // better.
               type = refinedVariableType(type, info, current);
@@ -753,8 +754,10 @@ function getVarDeclarations(info: TemplateInfo, path: TemplateAstPath): SymbolDe
 function refinedVariableType(
     type: Symbol, info: TemplateInfo, templateElement: EmbeddedTemplateAst): Symbol {
   // Special case the ngFor directive
-  const ngForDirective =
-      templateElement.directives.find(d => identifierName(d.directive.type) == 'NgFor');
+  const ngForDirective = templateElement.directives.find(d => {
+    const name = identifierName(d.directive.type);
+    return name == 'NgFor' || name == 'NgForOf';
+  });
   if (ngForDirective) {
     const ngForOfBinding = ngForDirective.inputs.find(i => i.directiveName == 'ngForOf');
     if (ngForOfBinding) {