fix(send-email/mailchimp): Handle queued email

[jnv]

Description

Mailchimp map expects the status of the message to be sent, however it can be also queued (as is the case of messages with attachments), so this fixes the map to handle sent, queued, or scheduled messages as successfully submitted.

Motivation and Context

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have read the CONTRIBUTING document.
• [x] I haven't repeated the code. (DRY)
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.