Aligned conversation media types with backend expectations

[GPaoloni]

Description

This PR fixes an existing issue where saving contacts fails with 500 error status code.
The issue arises because the conversation medias in the create contact payload were using the new format, but bundled in the legacy rawForm.conversationMedia property. This PR fixes the issue by moving this to the root of the create contact payload, where the backend expects the new format to be present.

Verification steps

• Start a new local HRM server in branch v2.10-rc.
• Start a new development Flex instance using this branch.
• Start a new chat contact and try saving it: it should succeed.
• Test that everything else around the fixes recently included in the RC branch are still working as intended.

[stephenhand]

LGTM - I made a lot of the same changes on master,