[ENHANCEMENT] Allow direct input and secure storage of an API key as an alternate auth flow

[justinwilaby]

Heroku front-end auth checks IP alignment which will yield an "IP Mismatch" error 100% of the time for containerized VSCode instances. Codespaces, Code Builder, etc. The workaround is to use heroku auth:login -i but this does not work when MFA is enabled.

This enhancement is to allow direct input of the Heroku API key and store it securely on containerized VSCode environments.

When containerization is detected by the extension, the user will be presented with an input dialog that accepts an API key obtained directly through the authorizations page or via the heroku auth:token command.

[git2gus]

This issue has been linked to a new work item: W-17973049