Issue #3200231 by davidjguru: Align naming in module

Summary

Gathering the related task with changes in naming of the module, from the history contained in Issue: #3200231.

Epic

This merge request owns to Epic #3200222

This set of commits

1. Changes naming in settings file (.settings.yml and .schema.yml).
2. Renames config object created for the module, from "lightweight_webform_mailchimp" to just "lwm".

For testing

Download and install the module. Then check strings and titles.