refactor: Switching backend to spf13/cobra

[mirac-cisco]

Description

Discussing with @sambetts-cisco, it seemed that it's better to switch backend's command parsing to also use spf13/cobra like the cli. The PR is just replacing one with the other, maintaining the same ENV parsing and same command structure.

New help:

VMClarity Backend

Usage:
  vmclarity-backend [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  run         Starts the server
  version     Displays the version

Flags:
  -h, --help      help for vmclarity-backend
  -v, --version   version for vmclarity-backend

Use "vmclarity-backend [command] --help" for more information about a command.

I've ran the make test which all pass, also manually confirmed that the ENV variables are correctly received. The behavior is identical as before.

Type of Change

[ ] Bug Fix
[ ] New Feature
[ ] Breaking Change
[x] Refactor
[ ] Documentation
[ ] Other (please describe)

Checklist

• I have read the contributing guidelines
• Existing issues have been referenced (where applicable)
• I have verified this change is not present in other open pull requests
• Functionality is documented
• All code style checks pass
• New code contribution is covered by automated tests
• All new and existing tests pass

[chrisgacsal]

LGTM!