tests: cover native VM module alias order

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Risky behavior now covered

• Native VM logical alias probing now has deterministic unit coverage for qagame -> game -> server, game/server, cgame/client, ui/frontend, reverse aliases, case-insensitive recognition, output limits, and custom-module fallback behavior.

Test files added/updated

• Updated tests/unit/test_vm_native_module.c with alias-order cases.
• Updated CMakeLists.txt so unit_vm_native_module links the minimal qcommon stubs and production Q_stricmp implementation.
• Updated tests/README.md to document the unit target.
• Extracted VM_BuildNativeModuleLoadOrder() into src/qcommon/vm_native_module.c and wired loadNative() to consume it, so tests cover the production ordering table.

Why this reduces regression risk

• Native module alias loading is a core compatibility path for full conversions and renamed native modules; a silent ordering/name regression can prevent game, cgame, or UI modules from loading and fall back unexpectedly.
• The test is pure, deterministic, and independent of filesystem or dlopen behavior while still exercising the production alias helper used by loadNative().

Validation

• cmake -S . -B build-coverage-tests -DBUILD_TESTING=ON -DBUILD_UNIT_TESTS=ON
• cmake --build build-coverage-tests --target unit_vm_native_module
• ctest --test-dir build-coverage-tests -R unit_vm_native_module --output-on-failure