Those property features don't seem to be in use anywhere.
They are redundant since the docs cover the same information
and more. They also created unnecessary translation work.

Closes #4904

Replace leftover gtk-doc syntax (#Type) with backquotes.

Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.

Use g_slist_free_full more consistently. This commit just converts
the obvious cases where g_slist_forall is directly followed by
g_slist_free.

Instead of Return value:

It is a little heavy handed. The text can speak for itself.

https://bugzilla.gnome.org/show_bug.cgi?id=702996

and use it

Mostly correcting it's to its and changing some , to .

That function can't be meant to be public, since it take
a GtkCellAreaBoxContext argument, which is not a public type.

Add a _gtk_orientable_set_style_classes() function so all
orientation changes to style happen in a single place.

This is so g_object_set() on that property leaves widgets' style in
a meaningful state. Fully fixes bug 639157.

They are private.

gtk/gtkcellareaboxcontext.h -> gtk/gtkcellareaboxcontextprivate.h

This was already done for the most part but not taken care
of for single cell groups (which is the most common case).

Now a cell can either have a "fixed" size or it can have
an "aligned" starting point or both. "fixed" size cells take
no space when they are invisible.

Whitespace fixes, comment formatting, etc

Added a few apis,

  - GtkCellAreaContext get_preferred_height_for_width &
    width for height apis and vfuncs, this lets the icon view
    request the collective (and aligned) height for width for
    a said row.

  - gtk_cell_area_copy_context() this creates a duplicate of
    an already created and requested context, this way the icon
    view uses a global context to request the widths of all rows
    and then makes a copy with all the stored alignments and
    uses a separate copy to calculate the height and alignments
    of each row separately.

cycling focus from row to row for a horizontal area we can remember
where focus was the last time around.

This allows us to reduce code allocation code paths in subclasses, as
a result GtkCellArea implements the ->render() vfunc and the subclass
only decides the cell area and background area distributions in a single
code path.

gtk_cell_area_foreach_alloc() itterates over an allocated list of cells
and calls a callback with the cell's allocation until the callback returns
TRUE.
  - Removed vfunc get_cell_allocation() and implemented
    gtk_cell_area_get_cell_allocation() using foreach_alloc()
  - Added gtk_cell_area_get_cell_at_position() using foreach_alloc()
  - Removed GtkCellAreaBox ->event() implementation and implemented
    mouse "click" cell activation in GtkCellArea class directly using
    gtk_cell_area_get_cell_at_position().

Also gave a boolean return value to the callback to allow breaking out of the loop.

the ->focus() method was getting mixed up when more than
one cell was in the same group (not aligned), added the
proper check to break out of the loop on time.

Changed GTK_CELL_AREA_WARN_INVALID_CHILD_PROPERTY_ID for GTK_CELL_AREA_WARN_INVALID_CELL_PROPERTY_ID