NC | ConfigFS | Create prepare for schema functions and some manage_nsfs refactoring

[romayalon]

Explain the changes

1. ConfigFS -
   1. Created _prepare_for_account_schema() and _prepare_for_bucket_schema() function that prepares a json config file to be written to the config dir.
   2. moved the preparation impl from the callers to the prepare functions called from create/update_account_config_file() and create/update_bucket_config_file().
2. CLI -
   1. Instead of calling write_stdout_response() from every action in the CLI, called it from the management functions.
   2. Removed account_management() and bucket_management().
   3. Removed old config file preparation code.
   4. moved name/access_key existence check from add_account()/update_account()/add_bucket()/update_bucket() to validate_account_args()/validate_bucket_args() in CLI validations.

Issues: Fixed #xxx / Gap #xxx

Testing Instructions:

• Doc added/updated
• Tests Updated

[shirady]

LGTM
(after adding the changes in discussion)