[DO NOT MERGE] Pass attachment name to GA4 details component tracking

[AshGDS]

What/Why

• On pages with attachments, all of the Request an accessible format details elements have the same GA4 title/section - they all pass Request an accessible format as their title/section when clicked.
• This means PAs can't tell which details component have been clicked, as they're all passing the same data.
• For example, see the attachments on https://www.gov.uk/guidance/prove-your-english-language-abilities-with-a-secure-english-language-test-selt
• Therefore this PR makes the section values the name of the attachment they are sitting under.

Visual Changes

None.

[andysellick]

@AshGDS can I check is this solution going to work on the page you linked to, as the attachment itself appears to be buried in govspeak and not something we can pass options to?

[AshGDS]

@andysellick Yeah, govspeak renders the attachment component, though the attachment component is what will be passing the title to the details component. The details component is rendered inside of the attachment component, so I think this should be OK as we don't need to pass anything ourselves, the attachment component does it for us.

It's difficult to test locally because in order to update the HTML on all these pages, we have to republish all our documents with attachments, so that govspeak regenerates the attachment component HTML.

See https://github.com/alphagov/govspeak/blob/df4d00a7e8d073a31677acf4e88093e157819b4d/lib/govspeak/post_processor.rb#L69

However, I've been asked to hold off on this change for now, so there's less need to review this.