Manage Variant Configuration in CLI

[devgenix]

This PR adds functionality in the CLI to allow manage App Variants configuration from the CLI.

The following Commands have been introduced;

Manage App Variant Configurations

• agenta config pull/agenta config pull <app_name.variant_name> -> Pull the configuration for all app variants belong to the app where agenta init was done or for a specific app variant, into a configuration file by the name of the respective variant(s) <app_name.variant_name>.toml
• agenta config update/agenta config update <app_name.variant_name> -> Updates the configuration for all app variants belong to the app where agenta init was done or for a specific app variant into the variant(s) configuration file

Add an App variant

• agenta variant add -> This command will list all the variants in the app and ask you to choose which one to use as the base for the new variant.

• agenta variant add --from <variant_name> -> Create a variant from an existing variant as the base

• agenta variant add --config_file app.<variant_name>.toml -> Add a new variant based on a valid toml configuration file

Every add variant command would pull the config file for the variant and save it after creating the variant.

The following existing commands have been enhanced;

• agenta variant delete -> would now also delete the configuration file associated with a variant, if present.
• agenta variant serve <file_name>.py/agenta variant serve --file_name <file_name>.py -> Would now pull the config file for the default variant created.

Other enhancements

Configuration check will now also pull the latest version of all variant configuration/remove config files for variants that have been deleted from the backend.