Adopted shared header for form submission page

[PaarthAgarwal]

Addresses #8539.
I have adopted shared header template for form submissions page.
As discussed with @lb- I have shifted form rows to the bottom of header.
Before:

After:

[squash-labs]

Manage this branch in Squash

Test this branch here: https://paarthagarwalform-submissions-bupzb.squash.io

[lb-]

I think maybe we can put the date fields outside the header completely.
Also the fields need to have the left / right margin removed so the content is all aligned to the side.

[lb-]

As discussed

• Let's try to bring the date fields back into the header fully (where they were before roughly) - it seems like this will be the path of least resistance
• Add a new way to add search_fields to the shared header template that also allows us to avoid passing in a search_url (as this form just submits to the view itself).
• Tweak the classes first to get pretty close and if needed add some custom CSS but see how you go by looking at the classes / layout of other headers first.

[lb-]

Closing in favour of #8862