Add support for ExposedPorts to the Image config

[baronfel]

This is a fairly mechanical transformation. Things remaining to do:

• tests to verify the addition of the default aspnetcore port declarations (or not, as appropriate)
• tests to verify deduping
• add warnings for malformed ContainerPort Items

[baronfel]

Part of #93 and #112

[baronfel]

For a test asp.net core container, we now have ExposedPorts:

"ExposedPorts": {
    "80/tcp": {}
}

and we can see the ports being automatically bound when -P is used:

➜ docker ps
CONTAINER ID   IMAGE                      COMMAND                  CREATED         STATUS         PORTS                   NAMES
a41168f7eac0   container-app-tres:0.0.4   "/app/container-app-…"   5 seconds ago   Up 4 seconds   0.0.0.0:49153->80/tcp   wonderful_faraday

and indeed, navigating to that port shows the app.

[benvillalobos]

overall lgtm, my biggest gripe is testing. Won't block on it if we need to merge & create an issue for that

[baronfel]

I made significant enough changes to the port parsing to warrant a re-review, but I did add a crap ton of testing to the core logic. Also went ham on the user-facing errors.

Large enough changes to warrant re-review.

[baronfel]

Rebased this on top of latest main - the only actual change was to flow ports through the containerize CLI, reusing the existing parse helpers to do CLI argument validation and flowing the validated values into Image creation inside the ContainerHelpers factory method.

[baronfel]

@benvillalobos when this merges we'll want to take care and make sure that the new tool task also handles writing port arguments to the CLI.