containertool: Arrange options into related groups

[euanh]

Motivation

Arranging related options together in groups makes it easier for users to find relevant options. This will be even more beneficial as more options are added (e.g. #91).

Modifications

• Arrange containertool's command line options into related groups with headings.
• Update build-container-image manual page to match the new groupings.

Result

• Users will be able to find help for specific options more easily.
• Grouping options together may also help them to discover new options related the tasks they are trying to achieve.

Test Plan

• No functional change.
• All existing tests continue to pass.

[euanh]

containertool command line help, for comparison:

% swift run containertool --help
[1/1] Planning build
Building for debugging...
[1/1] Write swift-version-1AF32027EA501FB9.txt
Build of product 'containertool' complete! (2.48s)
OVERVIEW: Build and publish a container image

USAGE: containertool [<options>] <executable>

ARGUMENTS:
  <executable>            Executable to package

SOURCE AND DESTINATION REPOSITORY OPTIONS:
  --default-registry <default-registry>
                          Default registry for image references which do not specify one
  --repository <repository>
                          Destination image reference
  --tag <tag>             Destination image tag
  --from <from>           Base image reference

IMAGE BUILD OPTIONS:
  --resources <resources> Directory of resources to include in the image

IMAGE CONFIGURATION OPTIONS:
  --architecture <architecture>
                          CPU architecture
  --os <os>               Operating system

AUTHENTICATION OPTIONS:
  --default-username <default-username>
                          Default username, used if there are no matching entries in .netrc
  --default-password <default-password>
                          Default password, used if there are no matching entries in .netrc
  --enable-netrc/--disable-netrc
                          Load credentials from a netrc file (default: --enable-netrc)
  --netrc-file <netrc-file>
                          Specify the netrc file path
  --allow-insecure-http <allow-insecure-http>
                          Connect to the registry using plaintext HTTP (values: source, destination, both)

OPTIONS:
  -v, --verbose           Verbose output
  -h, --help              Show help information.

[heckj]

I'm concerned I may have inadvertently been inconsistent. I tend to lean into "container image" vs. "image". I think 'destination' may be a bit overused, but it's super helpful where there's possible confusion of "where I'm getting a base image from" vs. "where I'm sending the built image" - take a look and see what you think. Hopefully this resonates well.

[euanh]

Thank you @heckj!