Add `bitops_unsigned_js_test.dart`, testing JS semantics with bit operations, and add `bitops_unsigned_shared_test.dart`, testing the semantics of bit operations in the subdomain (uint32) where the results coincide with webNumbers and with native numbers.
CoreLibraryReviewExempt: Is web specific, does have an area-web review.
Change-Id: I35ad1f78161a282780c3ec73da7823fee05c506c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/158014
Reviewed-by: Jake Macdonald <jakemac@google.com>
Reviewed-by: Stephen Adams <sra@google.com>
Reviewed-by: Lasse Nielsen <lrn@google.com>
Commit-Queue: Erik Ernst <eernst@google.com>
Erik Ernst