address a few esmodule TODOs

[connorjclark]

This PR is meant to be merged without squashing.

Going through some of the TODO(esmodules) comments, each commit here addresses a separate thing (so you should view each commit in isolation)

EDIT: converted to draft, a few unexpected test failures to dig through first

[connorjclark]

For some reason I can't get locales to work with a locally built devtools (only english is shown for all of devtools, not related to these changes). Should port the now-removed i18n test to e2e first before merging this.