Enable filtering of recipients on export of contact forms

Problem/Motivation

Contact forms can be configured to include multiple email address recipients. A typical export would be in the form:

langcode: en
status: true
dependencies: {  }
id: feedback
label: 'Website feedback'
recipients:
  - name1@example.com
  - name2@example.com
reply: ''
weight: 0

However, when creating a feature for general distribution, those specific recipients are likely not appropriate. The configuration should instead export as:

langcode: en
status: true
dependencies: {  }
id: feedback
label: 'Website feedback'
recipients: {  }
reply: ''
weight: 0

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes