Add support for defaults accounts/apps/environments

[auxesis]

Many commands require flags like --account-id, --app-id, and --environment to run.

This long form can be useful in scripts that run in CD pipelines, because they make it very explicit what's going on:

sectionctl deploy --account-id 2094 --app-id 7598 --environment production --directory commands/testdata/deploy/valid-nodejs-app/ --skip-delete

The flip side of this is that the local dev experience can be a clunky, because you need to specify the same arguments every time you run sectionctl:

sectionctl apps info --account-id 2094 --application-id 7598

This is particularly unergonomic for new users with a single account and a single app. The ideal experience should be running:

sectionctl apps info

and it runs successfully.

[AskAlice]

This has been implemented for deploy with #120 and was released in https://github.com/section/sectionctl/releases/tag/v1.11.1

I plan on making this a possibility for all commands later, using a kong resolver.