Move Runtime_125431 into the merged regression runner

Force optimized codegen with AggressiveOptimization instead of process-isolated tiered-compilation disabling, so the test can drop its standalone project and join Regression_ro_2.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: tannergooding

src/tests/JIT/Regression/JitBlue/Runtime_125431/Runtime_125431.cs

@@ -33,7 +33,7 @@ public static byte M43(Vector256<byte> arg1, ref byte[] arg2)
         return 0;
     }
 
-    [MethodImpl(MethodImplOptions.NoInlining)]
+    [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
     private static void Problem()
     {
         Vector256<byte> vr18 = Vector256.Create<byte>(0);

src/tests/JIT/Regression/JitBlue/Runtime_125431/Runtime_125431.csproj

@@ -95,6 +95,7 @@
     <Compile Include="JitBlue\Runtime_125169\Runtime_125169.cs" />
     <Compile Include="JitBlue\Runtime_125301\Runtime_125301.cs" />
     <Compile Include="JitBlue\Runtime_125328\Runtime_125328.cs" />
+    <Compile Include="JitBlue\Runtime_125431\Runtime_125431.cs" />
     <Compile Include="JitBlue\Runtime_126060\Runtime_126060.cs" />
     <Compile Include="JitBlue\Runtime_127260\Runtime_127260.cs" />
     <Compile Include="JitBlue\Runtime_127446\Runtime_127446.cs" />