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.

<!-- START COPILOT CODING AGENT TIPS -->
---

💡 You can make Copilot smarter by setting up custom instructions,
customizing its development environment and configuring Model Context
Protocol (MCP) servers. Learn more [Copilot coding agent
tips](https://gh.io/copilot-coding-agent-tips) in the docs.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>
Co-authored-by: Yong He <yonghe@outlook.com>
Co-authored-by: ArielG-NV <159081215+ArielG-NV@users.noreply.github.com>
Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

0 files changed, 0 insertions, 0 deletions