Heading added below media for MAP

[ryanmccombe]

Is your feature request related to a problem? Please describe.
The headline transformer always adds the heading to the start of the blocks

For MAPs, we want the media to be first

Describe the solution you'd like
Update the transformer to prevent it from adding a heading above the media player if the page is a MAP

It can add the heading below instead

Describe alternatives you've considered
N/A

Testing notes
[Tester to complete]

Dev insight: Will Cypress tests be required or are unit tests sufficient? Will there be any potential regression? etc

• This feature is expected to need manual testing.

Additional context
Add any other context or screenshots about the feature request here.

[pjlee11]

@ryanmccombe there are a11y requirements we should evaluate before just moving the headline below the AV player. I believe @greenc05 has been looking into this recently...

Update: #4150 has details on the investigation