Per-page settings for language selector, progress indicator, etc

### Description

Currently, we have the `GlobalPageSettings` type that defines some settings that can be configured for pages. As it stands, these can be configured for all layout-sets in `layout-sets.json`, which sets the configuration for all pages (even for non-pages such as instance selector, confirm and receipt). It is also now possible to override them per-layoutset in `Settings.json` for each layout-set.

We should also make these settings configurable per-page (at least most of them, it may be the case that `autoSaveBehavior` is difficult to change per-page). If these settings are set per-page, they should override whatever is set in `Settings.json` and `layout-sets.json`.

Making this into generic hooks should make it easier to expand these settings and allow for new settings that then can be set on either of these 3 levels, with proper inheritance and shadowing.

### Related issue(s)

- #1862

Start by reviewing GlobalPageSettings and the existing configuration in layout-sets.json and Settings.json, then read related issue #1862. Trace how these settings are inherited and overridden today. Done means page-level settings can override both broader configuration levels, with generic hooks supporting future settings and any limitations such as autoSaveBehavior documented.

Written by the indexing model from the issue text.