Add support for a vpc-in-zip (.vpz) virtual point cloud format

[uclaros]

Description

VPC files can become quite big and the ascii json format does not really help keeping the size down.
Now that we have support for reading remote .vpc files, the need for a smaller file size is more apparent.

This PR adds a .vpz format with a zipped .vpc, similar to how we have .qgz with a .qgs inside.

Support for writing those files in pdal_wrench is pending: PDAL/wrench#84

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[qgis-bot]

@uclaros
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[qgis-bot]

@uclaros

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[github-actions]

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[ViperMiniQ]

Suggested change

	if ( outputName.endsWith( ".vpc"_L1, Qt::CaseInsensitive ) || outputName.endsWith( ".vpc"_L1, Qt::CaseInsensitive ) )
	if ( outputName.endsWith( ".vpc"_L1, Qt::CaseInsensitive ) || outputName.endsWith( ".vpz"_L1, Qt::CaseInsensitive ) )

[uclaros]

🤦

[ViperMiniQ]

Should we care if there are multiple VPCs in the file? Can we not just grab first and return early? We are only reading the ZIP and are not error detecting/correcting. I believe other software also just use the first file that has the correct extension in similar situations.

No strong opinion.

However, if you'd still prefer to have the check instead of an early return, consider something like this instead of the loop:

const QStringList vpcFiles = dir.entryList( QStringList( "*.vpc" ), QDir::Files );
if ( vpcFiles.isEmpty() )
... 
else if ( vpcFiles.size() > 1 )
...

readFromFilename = dir.filePath( vpcFiles.first() );

[uclaros]

I prefer not to use the first vpc in case there are multiple, as that may not be obvious to the user that only a single vpc is being used.
I updated to use the suggested QDir::entryList :)