[cdac] Run unit tests + DataGenerator tests in runtime-diagnostics pipeline

Three pieces:

1. eng/Subsets.props: wire the DataGeneratorTests project
   (cdac/tests/DataGenerator/) under the existing tools.cdactests subset
   alongside the existing UnitTests project. No new subset -- one subset
   builds both managed-side cDAC test projects.

2. eng/pipelines/runtime-diagnostics.yml: new CdacUnitTests stage that
   runs tools.cdactests on linux_x64 Checked with -test. Independent of
   the dump/stress legs (no native runtime needed). Publishes xunit
   results. Now the cDAC unit tests + DataGenerator tests live in the
   cDAC-focused pipeline next to the dump/stress tests.

3. src/native/managed/cdac/tests/DataGenerator/TestTarget.cs: override
   the new Target.ReadNInt abstract method (added in e9e3c8d,
   #128784) so the DataGeneratorTests project compiles. Mirrors the
   existing ReadNUInt override.

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

Author: Max Charlamb

eng/Subsets.props

@@ -531,6 +531,7 @@
 
   <ItemGroup Condition="$(_subset.Contains('+tools.cdactests+'))">
     <ProjectToBuild Include="$(SharedNativeRoot)managed\cdac\tests\UnitTests\Microsoft.Diagnostics.DataContractReader.Tests.csproj" Test="true" Category="tools"/>
+    <ProjectToBuild Include="$(SharedNativeRoot)managed\cdac\tests\DataGenerator\Microsoft.Diagnostics.DataContractReader.DataGeneratorTests.csproj" Test="true" Category="tools"/>
   </ItemGroup>
 
   <ItemGroup Condition="$(_subset.Contains('+tools.cdacdumptests+'))">

eng/pipelines/runtime-diagnostics.yml

@@ -278,6 +278,30 @@ extends:
               continueOnError: true
               condition: failed()
 
+    #
+    # cDAC Unit Tests + DataGenerator Tests — managed-side tests that don't need a
+    # real runtime. Independent stage; runs on linux_x64 Checked on every trigger
+    # (PR/manual/schedule).
+    #
+    - stage: CdacUnitTests
+      dependsOn: []
+      jobs:
+      - template: /eng/pipelines/common/platform-matrix.yml
+        parameters:
+          jobTemplate: /eng/pipelines/common/global-build-job.yml
+          buildConfig: checked
+          platforms:
+          - linux_x64
+          jobParameters:
+            nameSuffix: CdacUnitTests
+            # tools.cdactests builds + tests both the cDAC UnitTests project
+            # and the DataGeneratorTests project (both wired under that subset
+            # in eng/Subsets.props).
+            buildArgs: -s clr.aot+clr.iltools+clr.corelib+clr.nativecorelib+libs.sfx+clr.toolstests+tools.cdac+tools.cdactests -c $(_BuildConfig) -test
+            timeoutInMinutes: 120
+            enablePublishTestResults: true
+            testResultsFormat: 'xunit'
+
     #
     # cDAC Dump Tests — Build, generate dumps, and run tests on Helix (single-leg mode)
     #

src/native/managed/cdac/tests/DataGenerator/TestTarget.cs

@@ -199,6 +199,9 @@ public override TargetCodePointer ReadCodePointer(ulong address)
     public override TargetNUInt ReadNUInt(ulong address)
         => new TargetNUInt(PointerSize == 8 ? Read<ulong>(address) : Read<uint>(address));
 
+    public override TargetNInt ReadNInt(ulong address)
+        => new TargetNInt(PointerSize == 8 ? Read<long>(address) : Read<int>(address));
+
     public override void Write<T>(ulong address, T value)
     {
         Span<byte> span = GetSpan(address, System.Runtime.CompilerServices.Unsafe.SizeOf<T>());