Whitelist DrainReclaimer+Slot.Depth/OnEnterForTest in TestPrivateFieldNames

These PascalCase internal fields can't satisfy the camelCase/ALL_CAPS private-
field rule: Depth is accessed via ref (Volatile.Read/Write(ref slot.Depth)), so
it must stay a field, and OnEnterForTest is the test seam. Add both to the
exception regex, matching the existing precedent for MMapDirectory+Chunk.
BasePtr/Length (same situation: ref-accessed field-like members of a nested
helper class).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: paulirwin

src/Lucene.Net.Tests/Support/TestApiConsistency.cs

@@ -38,7 +38,7 @@ public override void TestProtectedFieldNames(Type typeFromTargetAssembly)
         [TestCase(typeof(Lucene.Net.Analysis.Analyzer))]
         public override void TestPrivateFieldNames(Type typeFromTargetAssembly)
         {
-            base.TestPrivateFieldNames(typeFromTargetAssembly, @"^Lucene\.Net\.Support\.(?:ConcurrentHashSet|PlatformHelper|DateTimeOffsetUtil|Arrays|IO\.FileSupport)|^Lucene\.ExceptionExtensions|^Lucene\.Net\.Util\.Constants\.MaxStackByteLimit|^Lucene\.Net\.Search\.TopDocs\.ShardByteSize|^Lucene\.Net\.Store\.BaseDirectory\.(?:True|False)|^Lucene\.Net\.Store\.MMapDirectory\+Chunk\.(?:BasePtr|Length)$|CharStackBufferSize$");
+            base.TestPrivateFieldNames(typeFromTargetAssembly, @"^Lucene\.Net\.Support\.(?:ConcurrentHashSet|PlatformHelper|DateTimeOffsetUtil|Arrays|IO\.FileSupport)|^Lucene\.ExceptionExtensions|^Lucene\.Net\.Util\.Constants\.MaxStackByteLimit|^Lucene\.Net\.Search\.TopDocs\.ShardByteSize|^Lucene\.Net\.Store\.BaseDirectory\.(?:True|False)|^Lucene\.Net\.Store\.MMapDirectory\+Chunk\.(?:BasePtr|Length)$|^Lucene\.Net\.Support\.DrainReclaimer\+Slot\.(?:Depth|OnEnterForTest)$|CharStackBufferSize$");
         }
 
         [Test, LuceneNetSpecific]