Docker improvements

[whimsical-c4lic0]

This PR makes 3 changes

• Automatically generate default auth.json and config.json files similar to the windows build process instead of using the previously hard-coded values
• Specify the alpine version (should help to maintain consistent builds in the future when alpine has a new version)
• Add the tini init system as a best practice for containers

[melithine]

Might be worth making it pass hadolint while we're at it?

[melithine]

It would be nice if we suppressed warnings during the GHAs since at that point they just balloon the logs. I want to take a crack at clearing them up in the future, but by the time the GHAs run, the tag is already cut, so it's already too late to fix them for that release. I'll set up at an action that triggers on PRs in the future once we get the current crop handled.

[whimsical-c4lic0]

I'm not sure the best way to do this. As far as I can tell, the warnings are created by MSBuild. The dotnet publish command supports setting the verbosity (https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet-publish). We could set that to silent. It's hard to tell locally, but I don't think that affects the MSBuild output though.

[whimsical-c4lic0]

Sounds good. I can post an update with both of those changes later. Looks like hadolint only wants ADD changed to COPY and packages installed with apk to be pinned to a specific version.