Add and fix tests for QgsMapLayer::clone

[agiudiceandrea]

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[github-actions]

🪟 x64-windows — ⚠️ vcpkg failed before producing per-port logs

vcpkg returned a non-zero exit code but no port left a parseable buildtree. This usually means a portfile-execute abort (e.g. find_library REQUIRED, vcpkg_extract_source_archive download failure), or a vcpkg-internal error such as a missing tool or registry/baseline mismatch.

Look at the artifacts and the workflow log:

📑 Download full build-logs-x64-windows artifact · 🔧 Workflow run · 📌 Commit 6a93b1a