Add reading support for multi-overview VPC files

[uclaros]

Description

Instead of parsing overview assets by their "overview" id, we now parse them based on their "overview" role.
VPC files may contain multiple overviews per asset with arbitrary ids.
All assets with "overview" role are now considered as overviews, loaded and rendered when zoomed out.
QgsPointCloudLayer and QgsVirtualPointCloudProvider now have an overviews() method returning a list of all overviews, instead of a single one.

Support for generating such vpcs using pdal_wrench is pending: PDAL/wrench#86

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[qgis-bot]

@uclaros

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[github-actions]

🪟 Windows Qt6 builds

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(Built from commit 6cda337)

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(Built from commit 6cda337)

[github-actions]

Tests failed for Qt 6 (ALL_BUT_PROVIDERS - fedora)

One or more tests failed using the build from commit 0f70302

classified_render_overview

classified_render_overview

Test failed at testOverviewRender at tests/src/python/test_qgspointcloudclassifiedrenderer.py:496

Rendered image did not match tests/testdata/control_images/pointcloudrenderer/expected_classified_render_overview/expected_classified_render_overview.png (found 2947 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 - ubuntu)

One or more tests failed using the build from commit 0f70302

classified_render_overview

classified_render_overview

Test failed at testOverviewRender at tests/src/python/test_qgspointcloudclassifiedrenderer.py:496

Rendered image did not match tests/testdata/control_images/pointcloudrenderer/expected_classified_render_overview/expected_classified_render_overview.png (found 2947 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.