TableView is missing some features compared to ListView; so finding out
where we currently are (which row) and programmatic positioning on a
specific y coordinate of a specific row require some workarounds for now,
including helpers in PdfDocument.

TableView also assumes (and sporadically enforces) that all cells in a
column have the same width.  So we need a placeholder Item for each page.
This also helps with rotation: the placeholder is now as wide as the
window or the image, whichever is wider, and the "paper" is centered
within; thus there's always room to rotate it.

There's still some problem with setting contentY in goToPage() after
the page has been zoomed to a size larger than the window: the values
look correct, but it scrolls too far.

But on the plus side, horizontal scrolling works.  So now we attempt to
control the horizontal position too: NavigationStack tracks it, and can
go back to a previous position; and links can in theory jump to specific
positions and zoom levels, scrolling horizontally such that a specific x
coordinate is visible.

Includes minor UI tweaks to make it look better on iOS.

Change-Id: I643d8ef48ef815aeb49cae77dcb84c3682563d56
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

On iOS, the native FileDialog doesn't work, sharing doesn't work, and
packaging files along with the application requires manual effort; so
a PDF file in resources seems to be the easiest alternative to make
the examples demo-able.

QPdfDocument wants a file path, because it uses QFile; but we like
to use URLs in Qt Quick.  So it's a bit of an impedance mismatch,
there are several choices about when and where to do the conversion,
and it's hard to say which way is more correct.  This way happens
to work for now.

Also do the rest of the things necessary to get this working on iOS.

Change-Id: Icb8614d5eed2510f101aefba534ef80cf890518f
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

I would prefer to use the "import as" mechanism to allow the user to
customize prefixes rather than hard-coding them, actually; but
currently every QML type in the QtPDF module has a hard-coded Pdf prefix.

Change-Id: I4c00e7891c58e028280599d6089a821b9e285c1a
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

This enables searching a PDF for a text string and getting the
boundaries of the areas where it is found.  The boundaries are returned
as polygons intended to be rendered with PathMultiline.

PdfPageView is a QML component intended to be a drop-in viewer for use
in applications that need the most common PDF viewing functionality.
More advanced applications are free to use it as a starting point for
customization.

Task-number: QTBUG-77507
Task-number: QTBUG-77514
Change-Id: Id08ac30224e41b6cdfb9300cc4288d5750259f78
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

QQuickPdfDocument is a wrapper for QPdfDocument providing appropriate
QML API.

Task-number: QTBUG-77506
Change-Id: Ifa2ef50d3d31179f1955c2f673495e727b962bd1
Reviewed-by: Michal Klocek <michal.klocek@qt.io>