Change fields' type to be Rich Text Editor types

[GergiH]

Branched out from: IFRCGo/go-frontend#1011

@nanometrenat @teklal IFRCGo/go-frontend#931 (comment)
Please provide us with a list of fields which should be changed to be RTE types.

Checklist (after backend changes)

• adjust frontend to parts too, to handle the new RTE fields' HTML
• if frontend RTE implementation was done before this, adjust the serializers if needed

[teklal]

• Surge alerts, the "Message" field https://prddsgocdnapi.azureedge.net/notifications/surgealert/add/
  here the messages that are shared already most of the time have bulleted lists but they don't show on the frontend in the desired way
• in field reports people sometimes add links to the "source" field so it would be good to be able to support the sharing of links there and having them properly show as links on the frontend too
• snippets Provide a Rich Text Editor option for snippets #670

I'll add more when I think of other places.

[GergiH]

Duplicate of: #670