FI-2338: New Dockerfile for validator

[dehall]

Summary

This PR replaces the dockerfile for the HL7 validator service with a new one intended to be deployed to Docker Hub, plus a short README explaining what it is and how to deploy it. I don't think end users should ever really have to worry about this, it's just for the dev team.

There are a few reasons we want our own wrapper around the HL7 validator wrapper service:

1. The service reaches out to the internet to fetch IGs, so MITRE developers need to add the MITRE certs
2. The official image is not a multi-arch build, it's currently amd64 only
3. This approach allows much cleaner version management compared to a per-repo Dockerfile like the original Dockerfile.fhir_resource_validator
4. It allows us to release "known good" versions so that test kits can safely point to latest

The image just fetches and runs a release JAR from the official repo, since JARs are platform-independent. Most of the rest is just copied from the official Dockerfile to ensure it's a drop-in replacement with the official image (i.e., the username "ktor", the file paths, and the run args). To minimize changes going forward, it takes the version number as a build argument, so we can push new versions of the image without code changes.

Testing Guidance

I haven't actually pushed the image yet since we should be sure we agree on the name & details first.

To try running the command in the readme without pushing to docker hub you can change the --push near the end to --load

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.68%. Comparing base (fd6771c) to head (bf61257).

Additional details and impacted files

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  Misses       1967     1967           
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Flag	Coverage Δ
backend	93.90% <ø> (ø)
frontend	70.77% <ø> (ø)

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[Jammjammjamm]

Could you stick this in a little script so we don't have to copy/paste it?

[dehall]

Added a script with the version number as a required command-line arg