(core) Use unicode-aware comparisons for user-visible strings.

Summary:
- Switch code that compares user strings to use localeCompare() based on Intl.Collator.
- Use en-US locale for now. (Ideally should be a document property.)
- Note that with this change, sorting is also becoming case-insensitive (which
  seems an improvement)

- Updated a sorted test fixture
- Updated a browser test with lots of unicode to expect different order.
- Added a bit of unicode to test ordering in Reference autocomplete dropdown.

Test Plan: Fixed / updated tests

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2758

app/client/lib/ACIndex.ts

@@ -7,7 +7,7 @@
  * "lush" would only match the "L" in "Lavender".
  */
 
-import {nativeCompare, sortedIndex} from 'app/common/gutil';
+import {localeCompare, nativeCompare, sortedIndex} from 'app/common/gutil';
 import {DomContents} from 'grainjs';
 
 export interface ACItem {
@@ -80,7 +80,7 @@ export class ACIndexImpl<Item extends ACItem> implements ACIndex<Item> {
       }
     }
 
-    allWords.sort((a, b) => nativeCompare(a.word, b.word));
+    allWords.sort((a, b) => localeCompare(a.word, b.word));
     this._words = allWords;
   }