Upgrade to Smithy 1.27.2 (#2226)

* Upgrade to Smithy 1.27.1

* Fix bugs exposed by 1.27.1

* Fix rules engine customization

* update rfc3339 parsing test

* refactor timestamp format & remove upstreamed test

* Update changelog

* rename test

* fix datetime parsing on server and clients

* fix up a few more failing tests

* precommit lints

* Fix bad merge