(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/common/gutil.ts

@@ -444,6 +444,11 @@ export function nativeCompare<T>(a: T, b: T): number {
   return (a < b ? -1 : (a > b ? 1 : 0));
 }
 
+// TODO: In the future, locale should be a value associated with the document or the user.
+export const defaultLocale = 'en-US';
+export const defaultCollator = new Intl.Collator(defaultLocale);
+export const localeCompare = defaultCollator.compare;
+
 /**
  * A copy of python`s `setdefault` function.
  * Sets key in mapInst to value, if key is not already set.