Guard COM teardown and de-duplicate native test helpers

[Copilot]

Verifies three review findings in the SimModelNative Google Test suite and applies minimal, test-only fixes. All three were still valid.

COM apartment teardown (TestEnvironment.cpp)

• ComEnvironment called CoUninitialize() unconditionally, tearing down the apartment even when CoInitialize failed (e.g. RPC_E_CHANGED_MODE).
• SetUp() now records success; TearDown() only uninitializes when initialization actually succeeded.

void SetUp() override { _comInitialized = SUCCEEDED(CoInitialize(NULL)); }
void TearDown() override
{
   if (_comInitialized) { CoUninitialize(); _comInitialized = false; }
}

Duplicated test data (RcmSpecs.cpp)

• should_return_valid_permutation_for_ten_node_example rebuilt the 10×10 adjacency matrix inline; it now reuses the existing createTenNodeMatrix() helper.

Duplicated extender class (TableFormula*Specs.cpp)

• The identical ValuePoints() / CallCacheValues() wrapper was redefined in three spec files (TableFormulaExtender, TableFormulaForOffsetExtender, TableFormulaForXArgumentExtender).
• Extracted into a shared src/TableFormulaTestExtender.h (TableFormulaTestExtender), now included by all three specs and registered in the .vcxproj. The CMake build resolves it via relative include.

Notes

• A full build was not run: git submodules and native NuGet packages are unavailable in this environment.