Fix FunctionReflection getName() returning null for overloaded functions (#8113)

When using Slang reflection API to find functions by name in a type,
`FunctionReflection::getName()` would return `nullptr` for overloaded
functions instead of the expected function name.

The issue occurred in `spReflectionFunction_GetName` when
`findFunctionByNameInType` returned a `SlangReflectionFunction` wrapping
an `OverloadedExpr` (for overloaded functions) instead of a single
`DeclRef<FunctionDeclBase>`. The `convertToFunc()` function would fail
for `OverloadedExpr` objects, causing `getName()` to return `nullptr`.

**Example of the bug:**
```cpp
// This code would fail before the fix
public interface IBase {
    public void step(inout float f);
}

public struct Impl : IBase {
    public void step(inout float f) { f += 1.0f; }
}

// Using reflection API:
auto implType = reflection->findTypeByName("Impl");
auto stepFunction = reflection->findFunctionByNameInType(implType, "step");
auto name = stepFunction->getName(); // Would return nullptr
```

**Fix:**
Modified `spReflectionFunction_GetName` to handle overloaded functions
by falling back to the name of the first overload candidate when
`convertToFunc` fails. This follows the same pattern already used by
`spReflectionFunction_specializeWithArgTypes`.

The fix ensures that:
- Overloaded function containers return the correct function name
- Individual overload candidates also return their names correctly  
- Non-overloaded functions continue to work as before
- No regression in existing functionality

**Testing:**
Added comprehensive test cases covering both the original issue scenario
and explicit function overloading. All existing reflection tests
continue to pass.

Fixes #8047.

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Co-authored-by: ArielG-NV <159081215+ArielG-NV@users.noreply.github.com>
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Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/slang-unit-test/unit-test-function-lookup-resolution.cpp b/tools/slang-unit-test/unit-test-function-lookup-resolution.cpp
index 539c9ac48..c88ca7760 100644
--- a/tools/slang-unit-test/unit-test-function-lookup-resolution.cpp
+++ b/tools/slang-unit-test/unit-test-function-lookup-resolution.cpp
@@ -75,6 +75,9 @@ SLANG_UNIT_TEST(functionLookupResolution)
     auto func1 = layout->findFunctionByNameInType(type, "method");
     SLANG_CHECK_ABORT(func1->isOverloaded());
     SLANG_CHECK(func1->getOverloadCount() == 3);
+    // Test that overloaded function containers return the correct name
+    SLANG_CHECK(func1->getName() != nullptr);
+    SLANG_CHECK(String(func1->getName()) == "method");
     if (func1->isOverloaded())
     {
         List<slang::FunctionReflection*> candidates;