Merge pull request #28914 from mike-north/ember-handlebars-consistency

[ember] don't re-create Handlebars.SafeString

types/ember__string/ember__string-tests.ts

@@ -1,4 +1,5 @@
 import { dasherize, camelize, capitalize, classify, decamelize, htmlSafe, loc, underscore, w } from '@ember/string';
+import { SafeString } from 'handlebars';
 
 dasherize(); // $ExpectError
 dasherize('blue man group'); // $ExpectType string
@@ -31,3 +32,7 @@ capitalize('', ''); // $ExpectError
 loc(); // $ExpectError
 loc("_Hello World");  // $ExpectType string
 loc("_Hello %@ %@", ["John", "Smith"]);  // $ExpectType string
+
+const handlebarsSafeString: SafeString = htmlSafe('lorem ipsum...');
+htmlSafe('lorem ipsum...'); // $ExpectType SafeString
+const regularString: string = htmlSafe('lorem ipsum...'); // $ExpectError