[Virtual Point Clouds] Add slider to adjust the switching between rendering overview only and sub index rendering

[ViperMiniQ]

This PR adds a slider that controls the point of switching between rendering overview only and rendering a sub index of the VPC.

The slider is more aggressive going to the right, less aggressive going to the left.

On 2D map canvas, if the average extent width of the sub indexes multiplied by the value from the slider is higher than the viewable map canvas, a sub index is loaded, otherwise overview only gets rendered.

Similarly, in the 3D Map, multiplier is applied on the sub index bounding box and if the camera is located within the box, sub index is fully loaded and rendered, if the camera is outside the box, overview only is rendered.

One change is that when all the sub indexes are shown in the 3D Map, we disable overview rendering to save resources.

[github-actions]

Tests failed for Qt 6 (ALL_BUT_PROVIDERS - ubuntu)

One or more tests failed using the build from commit a9eb485

virtual_pointcloud_3d_overview (testPointCloud3DOverview)

virtual_pointcloud_3d_overview

Test failed at testPointCloud3DOverview at tests/src/3d/testqgspointcloud3drendering.cpp:619

• Rendered image did not match tests/testdata/control_images/3d/expected_virtual_pointcloud_3d_overview/default/expected_virtual_pointcloud_3d_overview.png (found 745 pixels different)
• Rendered image did not match tests/testdata/control_images/3d/expected_virtual_pointcloud_3d_overview/qt6/expected_virtual_pointcloud_3d_overview.png (found 745 pixels different)

The full test report (included comparison of rendered vs expected images) can be found here.

Further documentation on the QGIS test infrastructure can be found in the Developer's Guide.

[github-actions]

Tests failed for Qt 6 (ALL_BUT_PROVIDERS - fedora)

One or more tests failed using the build from commit a9eb485

virtual_pointcloud_3d_overview (testPointCloud3DOverview)

virtual_pointcloud_3d_overview

Test failed at testPointCloud3DOverview at tests/src/3d/testqgspointcloud3drendering.cpp:619

• Rendered image did not match tests/testdata/control_images/3d/expected_virtual_pointcloud_3d_overview/default/expected_virtual_pointcloud_3d_overview.png (found 745 pixels different)
• Rendered image did not match tests/testdata/control_images/3d/expected_virtual_pointcloud_3d_overview/qt6/expected_virtual_pointcloud_3d_overview.png (found 745 pixels different)

The full test report (included comparison of rendered vs expected images) can be found here.

Further documentation on the QGIS test infrastructure can be found in the Developer's Guide.

[github-actions]

🪟 Windows Qt6 builds

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(Built from commit fad63e4)

🍎 MacOS Qt6 builds

Download MacOS Qt6 builds of this PR for testing.
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(Built from commit fad63e4)