Add test for generic-arity stripping in nested inferred type names (#1022)

Covers the BUG-4 fix in GetInferredLuceneTypeName (commit 9fc36a4) where the
back-tick arity is stripped from each enclosing declaring-type name, not just
the leaf, so a type nested under a generic outer (PairOutputs<A,B>.Pair) infers
"PairOutputs.Pair" rather than "PairOutputs`2.Pair". This test lives in the main
Lucene.Net test project alongside the other GetInferredLuceneTypeName cases,
since the change is in the shipping Lucene.Net assembly.

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

Author: paulirwin

src/Lucene.Net.Tests/Support/Reflection/TestReflectionTypeExtensions.cs

@@ -2,6 +2,7 @@
 using Lucene.Net.Index;
 using Lucene.Net.Search;
 using Lucene.Net.Util;
+using Lucene.Net.Util.Fst;
 using NUnit.Framework;
 using System;
 
@@ -41,6 +42,7 @@ public void TestGetLuceneTypeInfo_PackageNames(Type luceneNetType, string expect
         [TestCase(typeof(Field), "Field")] // test package mapping attribute
         [TestCase(typeof(ReferenceContext<>), "ReferenceContext")] // this type doesn't actually exist in Lucene, but it tests the generic type erasure
         [TestCase(typeof(FieldCache.CacheEntry), "FieldCache.CacheEntry")] // test nested type
+        [TestCase(typeof(PairOutputs<object, object>.Pair), "PairOutputs.Pair")] // nested type under a generic outer: arity stripped from the enclosing name too
         [TestCase(typeof(IAttribute), "Attribute")] // test interface
         public void TestGetInferredLuceneTypeName(Type luceneNetType, string expectedName)
         {