feat(ffi): unwind safety: shield FFI entrypoints with panic guard (#546)

This PR implements widely accepted Rust programming practices for
dealing with panics across ABI (programming language) boundaries.

- Add panic_guard.rs to wrap FFI calls and prevent panic across FFI/ABI boundary (undefined behavior).
- Capture per-thread backtraces via a temporary panic hook
- After a panic, subsequent invocations are poisoned.
- Integrate with_unwind_guard across the engine, schema registry, and target registry exportis

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

bindings/csharp/Regorus/Compiler.cs

@@ -177,7 +177,7 @@ namespace Regorus
                 if (result.status != Internal.RegorusStatus.Ok)
                 {
                     var message = StringFromUTF8((IntPtr)result.error_message);
-                    throw new Exception(message ?? "Unknown compilation error occurred");
+                    throw result.status.CreateException(message);
                 }
 
                 if (result.data_type != Internal.RegorusDataType.Pointer || result.pointer_value == null)