[OPT-7068] Update the email digest modal

Context:

To allow user to better manage the email digest, some improvements have to be added to the process configuration modal.

AT:

update the header, labels, label in the process 3 dots menu, etc
Allow user to select:
- one recipient in C7
- multiple recipients in C8 Saas
- recipients should be sent in an array (even if its just one)
Add schedule fields
Add test button "Send digest example to myself"

1.	Add schedule fields to email digest modal	Open	Unassigned
2.	Handle multiple recipients in email digest modal	Open	Unassigned
3.	Add Send digest example email button	Open	Unassigned

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