GPU: Replace assertions with error counters in ZS decoding.

[fweig]

Harden ZS decoding against malformed input. Remove debug assertions and instead always check for errors at runtime and set the corresponding GPU error counters.

[github-actions]

REQUEST FOR PRODUCTION RELEASES:
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The following labels are available
async-2023-pbpb-apass4
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async-2024-PbPb-apass1
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async-2024-PbPb-apass2
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[alibuild]

Error while checking build/O2/fullCI_slc9 for 3fde415 at 2025-10-17 19:12:

## sw/BUILD/O2-latest/log
ninja: build stopped: subcommand failed.

Full log here.