CLI: fix support for env vars when running dev/build commands

[joshbolduc]

Closes #21055

What I did

Fixed the target of the getEnvConfig call to reference an object that is subsequently passed to the dev/build helper functions. getEnvConfig was previously updating program, which appears to be a carryover from the old implementation where options were actually being read from program. Since options are now being passed to the dev/build functions directly, any options derived from environment variables were effectively being ignored.

(It also appears the logic to convert a string port value to a number was also effectively going unused, but as far as I can tell, it didn't matter.)

How to test

1. Create any sandbox
2. Within the sandbox, run yarn storybook with env vars. e.g.,
   • CI=true yarn storybook should not open a browser or prompt if there is a port conflict
   • SBCONFIG_PORT=8888 yarn storybook should start storybook on port 8888

Not sure a good way to add a test for this behavior?

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[sheriffMoose]

Tested & Verified, I just removed the appliedOptions variable as it is not actually needed. I will push another commit to fix the same issue for angular apps

[valentinpalkovic]

@ndelangen

Can we merge this one?