xtended hideAppNameInPdf to be hidden or visible depending on which layoutSet is used when generating the PDF.

### Description

Direktoratet for byggkvalitet wants the ability to define which layoutSets should display the app name in PDF generation. This is because some users only submit subforms, where including the app name can be misleading, while the main form—submitted by another user—should include the app name in the PDF.

There are alternative ways to achieve this today. One option is to hide the app name entirely by setting `hideAppNameInPdf: true` and instead add a header component in the relevant custom PDFs. Another option is to use a dynamic boolean expression in `hideAppNameInPdf`, combined with custom logic to define a data model field that controls whether the app name should be shown or hidden.

### Additional Information

Relevent app: https://altinn.studio/repos/dibk/et-v4/src/branch/master/App/ui/layout-sets.json
Slack thread: https://digdir-samarbeid.slack.com/archives/C02EJ9HKQA3/p1781856267840309

Start by reviewing the referenced dibk/et-v4 layout-sets.json to understand how layout sets are defined, then trace the PDF-generation entry points that consume those settings. Done means users can configure app-name visibility per layoutSet while preserving the existing behavior for forms that do not use the new setting.

Written by the indexing model from the issue text.