feature/ISTWCMS-5471-ocardena: migrate mailchimp blocks

Merged Ozle Cardenas requested to merge feature/ISTWCMS-5471-ocardena-migrate-mailchimp-block into 1.0.x

Summary of changes:

  1. Add new migration file uw_cbl_mailchimp for mailchimp blocks.
  2. Add new migration source UwMailchimp to get all ckmailchimp tags on mapped fields.
  3. Add the new blockuw_cbl_mailchimp to UwBlockLookup and UwMigrateTrait.

Merge request reports