Update depends_on and atmos describe dependents

[aknysh]

what

• Update depends_on and atmos describe dependents
• Restore checking for the context in imports with Go templates removed in Add overrides section to Atmos stack manifests. Update docs #464
• Update README

why

• The settings.depends_on was incorrectly processed for cross-tenant, cross-environment and cross-staging dependencies
• When the context was not provided in imports with Go templates, we did not process Go templates. A change was introduced in Add overrides section to Atmos stack manifests. Update docs #464 which does not work for all use-cases. Restoring the old functionality