Add expression functions for returning User and Project Bookmark

[bogind]

Description

Replacing #63613
As suggested by @nirvn the PR allows access to both Project and User(profile) bookmarks in the expression engine as functions:

1. project_bookmark - takes 1 parameter, the bookmark name and returns a map object with the properties described below
2. user_bookmark - similar to project_bookmark but for User Bookmark, so it uses the QgsApplication bookmark manager.

The returned maps\objects are structured to allow access to the following properties of the returned bookmark:

1. name
2. id
3. group
4. extent - a polygon geometry
5. extent_rect - an object containing
   5.1. x_min
   5.2. y_min
   5.3. x_max
   5.4. y_max
6. width
7. height
8. crs
9. rotation

The idea behind the changes are to allow users to use bookmark properties to set specific data driven overrides as well as display them.

The changes are:

1. In QgsProject added GetNamedUserBookmark and GetNamedProjectBookmark to return a named bookmark and registered both under QgsProject::createExpressionContextScope()
2. Registered both functions in QgsExpressionContextUtils under QgsExpressionContextUtils::registerContextFunctions
3. Added JSON help files for both under resources/function_help/json

Built successfully without issues on Windows 11 with QT6 using OSGeo4W qgis-qt6-dev-deps and MS Visual Studio 2022.

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[bogind]

Hi @nirvn
could you maybe take a look at the implementation I did here?
I tried to do as you suggested (back in November) and added access to the bookmarks via a function and not variables in as close a way as I could to what is done with project_color_object.

I am just now seeing that you also asked me to name the functions *_bookmark_details but I hope they can still be clear enough as *_bookmark.