[MaxRev-Dev]

Summary

Pin SWIG 4.4.1 across Linux, macOS, and Windows package builds so each platform generates the same C# API surface.

• keep the SWIG version and source checksum in shared/swig.lock
• build checksum-verified SWIG from source on Unix platforms
• install the locked Chocolatey version on Windows and fail if another version remains active
• invalidate platform build caches when the shared SWIG lock changes
• update local build prerequisites and stable PATH guidance

Context

This addresses the ABI consistency concern raised in OSGeo/gdal#15079. SWIG versions below 4.2 do not support the C# cs:defaultargs feature used by that bindings overhaul, which could otherwise give the same NuGet package version a different API surface on Linux.

Tests

• built and ran the locked SWIG version from a clean temporary prefix on macOS
• built the Debian 12 base stage and verified swig -version reports 4.4.1
• passed ShellCheck and shell syntax validation
• passed PowerShell parser and shared-lock parsing validation
• parsed the modified GitHub Actions workflows as YAML
• passed Dockerfile build checks (apart from an existing keyword-casing warning in ci/Dockerfile.vcpkg)