Add a page picker for the PageReference parameters of the Edit Macro dialog

The include and display macros have a deprecated page parameter, an alternative to their reference parameter. It is hidden from the Edit Macro dialog of a new macro, but shown when an existing macro sets it, like {{include page="Sandbox/TestPage1"/}}, the first example of the include documentation. It is declared with the PageReference display type, which has no picker, so the dialog shows a plain text field next to the page picker of the reference alternative.

The parameters are hidden for this very reason, as the comment above setPage in IncludeMacroParameters.java says: "ATM we don't have a picker for PageReference types". The display macro does the same in DisplayMacroParameters.java.

The improvement is a page picker for the PageReference display type, an html_displayer template for pagereference reusing the picker of documentreference. The priority is low: most users never see the deprecated parameter, and only these two parameters use the type. XWIKI-25477 covers the other problem of the same case, the two fields with the same name and description.

KOs covered

Impact found on macro fluidity

These 2 minor KOs come from the WYSIWYG usability audit of the macros, under the criterion C4 input-assistance of its usability criteria, which asks that each parameter uses an appropriate input, such as a picker. The page of each macro, linked in the table, has the full notes.