* Fix import mapping to work with built JS files
This allows us to ship a Docker image that runs using `node` directly,
rather than via `tsx`.
* Remove use of top-level `await` expressions
These were only used in tests and weren't critical. Switch away so we
have the optional to convert to CommonJS if we need.
* Switch all imports to use relative paths instead of ~ shortcut
The ~ shortcut doesn't work in some contexts, which makes our lives more
difficult when trying to output ESM.
Since we were already using relative paths in some part of the codebase
and not others, just switch to using relative paths everywhere for
simplicity.
* Switch imports to append .js extension
And update Jest configuration to work with this extension.
* Build single image instead of two separate ones
We originally created the other image so that we could build an image
using only packages published to NPM, but this proved problematic when
wanting to test those changes without publishing.
Since there are more situations where we'd want to ship an image using
unpublished packages (i.e. for testing) remove the "public" image and
update our "testing" image to also be used as the public image. However,
a key difference is that the testing image will now run compiled JS
instead of using a TypeScript interpreter.
