GeezerVison

Summary

Backports and adapts the full native Azure Linux 4 packaging change from #28107 (d8984870ca158442c0c043653ee63cef920ace8c) directly to release/v7.6.7.

• Generates distinct framework-dependent Azure Linux 3 (.cm) and Azure Linux 4 (.azl4) RPMs for x86_64 and aarch64, including Release: 1.azl4 metadata.
• Replaces the Azure Linux 4 beta mappings added by [release/v7.6.7] Add Azure Linux 4 RPM support #28039 with explicit preview and stable mappings for both architectures. The logical mapping names omit -yum because the PMC publishing Run.ps1 appends it.
• Keeps all four Azure Linux 3 .cm mappings unchanged.
• Hardens both RPM filename validators by escaping literal dots, anchoring complete filenames, and accepting azl4.
• Adds targeted coverage for artifact names, RPM Release metadata, dependencies, mapping channel policy, retained Azure Linux 3 mappings, and malformed filenames.

PowerShell 7.6 dependency adaptation

The master change in #28107 uses the .NET 11 runtime contract. PowerShell 7.6 targets .NET 10, so this backport deliberately preserves the branch's Azure Linux native dependency set and requires dotnet-runtime-10.0 only for framework-dependent cm and azl4 RPMs. It does not introduce any .NET 11 dependency.

Relationship to #28039

#28039 is already merged in release/v7.6.7. It added initial Azure Linux 4 PMC routing using the existing .cm RPM and updated the shared dependencies to the .NET 10 contract. This PR builds on that work: it creates native .azl4 packages, separates preview/stable routing, and adds the validator and test hardening from #28107.

Validation

• Pester 5.6.1: 32 targeted packaging and Linux package-name tests passed.
• Parsed tools/packaging/packaging.psm1 and both changed Pester files with the PowerShell parser.
• Parsed tools/packages.microsoft.com/mapping.json with ConvertFrom-Json.
• git diff --check passed.