feat(core): map 'for' attribute to 'htmlFor' property (#10546)

This improves ergonomics a bit by allowing people to write:
`<label [for]="ctxProp"></label>`.
This is similar to the existing class -> className mapping.

Closes #7516

modules/@angular/compiler/src/schema/dom_element_schema_registry.ts

@@ -231,6 +231,7 @@ const SCHEMA:
 
 const _ATTR_TO_PROP: {[name: string]: string} = {
   'class': 'className',
+  'for': 'htmlFor',
   'formaction': 'formAction',
   'innerHtml': 'innerHTML',
   'readonly': 'readOnly',