This fixes all the "Injection of parameters into signal handlers
is deprecated. Use JavaScript functions with formal parameters instead."
warnings.

Qt3D.Extras cannot be updated to 2.6 yet, otherwise there are errors.

With Qt6, OpenGL is not used directly anymore, and we thus must use
the RHI backend, set to version 1.0.

The SphericalHarmonics shaders, which were previously written in OpenGL,
need to be updated accordingly.

Call the `QGeometry` objects from the correct module, and initialize
correctly the Camera object upon the construction of the
TrackballController object.

Additionally harmonize comments and explicitly declare parameters
for slots that need them.

`PointSize` is not supported by RHI.

The fit must be automatically triggered when the size of the image
changes. In case the image size remains the same but the orientation tag
is updated, this means that the displayed size of the image has changed
(with the orientation taken into account, the width and height might end
up being inverted), so the fit should also be triggered.

Disable and hide the wireframe mode as the shaders need to be updated
for RHI.

When converting the `StatusData` to a dictionary, only data attributes
should be stored in said dictionary. With Qt6, the `objectNameChanged`
signal, of type `SignalInstance`, is added to the dictionary. It needs
to be removed manually as it is not JSON-serializable. Otherwise,
the nodes cannot be computed anymore.

Replace `DiffuseSpecularMaterial`, which does not seem to support
correctly textures anymore, with `DiffuseMapMaterial`.

…with

`QtQuick.Window` does not exist anymore with Qt6. QQuickWindow is now
directly part of the QtQuick module.

When the SequencePlayer isn't available (when QtAliceVision has not been
loaded), the `viewer` element is null. All accesses to properties of this
object should thus be prevented.

This prevents crashes when the project is done loading but
`Application` is not yet ready.

QMouseEvent::x() and QMouseEvent::y() have been marked as deprecated and
should be replaced with QMouseEvent::position().x() and
QMouseEvent::position().y().

The curve scale of the mouse area for an edge used to be defined when
initializing the `EdgeMouseArea` for that edge. Setting it triggers a
chain of event that allow the mouse area to be active, thus correctly
detecting when it is being hovered or clicked on.

With Qt6, these events unfolded before the `EdgeMouseArea` had finished
initializing, which then caused it to not be active until the edge's
shape was modified (and the chain of events triggered again). It is now
set once the component has been created, so all the events can happen
in an environment where they are taken into account.

The callbacks of `childrenRepeater` (which was used to "fill"
`ListAttributes` with children) were not correctly set. Their prototypes
were missing the `index` argument, meaning that instead of being
provided with the child attribute that was added or deleted,
they were provided with its index in the model.

The added children attributes were also instatiated as empty attribute
pins that were still visible, thus increasing indirectly the spacing of
the initial pin.

Use a single light entity instead of one per camera.
Use directional light instead of point light.
Add camera relative directional light controller.

Default camera up should be accurate and consistent with camera view center.
Default camera up vector is not refresh or checked when default camera view center is set.