Wire Runtime_129076 into Regression_ro_2 merged runner

Drop the standalone .csproj and add the .cs to Regression_ro_2.csproj
following the pattern of recent JitBlue tests (Runtime_128631,
Runtime_128801). Standalone csprojs are only needed when the test
requires its own process via CLRTestEnvironmentVariable; ours doesn't.

Verified: bash Regression_ro_2.sh invokes Runtime_129076.TestEntryPoint
(passes on the fixed JIT, fails on the regressed JIT).

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

Author: AndyAyersMS

src/tests/JIT/Regression/JitBlue/Runtime_129076/Runtime_129076.cs

@@ -7,6 +7,8 @@
 // so downstream uses comparing the value arithmetically (here `~v3 >= -1`)
 // folded the wrong way.
 
+namespace Runtime_129076;
+
 using System.Runtime.CompilerServices;
 using Xunit;
 

src/tests/JIT/Regression/JitBlue/Runtime_129076/Runtime_129076.csproj

@@ -100,6 +100,7 @@
     <Compile Include="JitBlue\Runtime_127446\Runtime_127446.cs" />
     <Compile Include="JitBlue\Runtime_128631\Runtime_128631.cs" />
     <Compile Include="JitBlue\Runtime_128801\Runtime_128801.cs" />
+    <Compile Include="JitBlue\Runtime_129076\Runtime_129076.cs" />
   </ItemGroup>
   <Import Project="$(TestSourceDir)MergedTestRunner.targets" />
 </Project>