fix: add --local support for login

[shazron]

Motivation and Context

This allows the login access tokens to be saved locally to the project, instead of globally for the user.

How Has This Been Tested?

• npm test
• aio login --local on one project in stage
• aio login --local on another project in prod
• aio app deploy for both projects simultaneously, both should succeed

This can be used for projects that need to be logged in different Orgs (not just prod/stage).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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