[mlir:LSP] Link the test dialect into mlir-lsp-server

This allows for more easily interacting with lit files that utilize
the test dialect.

mlir/tools/mlir-lsp-server/CMakeLists.txt

@@ -21,6 +21,7 @@ if(MLIR_INCLUDE_TESTS)
     MLIRTestPass
     MLIRTestReducer
     MLIRTestRewrite
+    MLIRTestTransformDialect
     MLIRTestTransforms
     )
 endif()

mlir/tools/mlir-lsp-server/mlir-lsp-server.cpp

@@ -13,8 +13,19 @@
 
 using namespace mlir;
 
+#ifdef MLIR_INCLUDE_TESTS
+namespace test {
+void registerTestDialect(DialectRegistry &);
+void registerTestTransformDialectExtension(DialectRegistry &);
+} // namespace test
+#endif
+
 int main(int argc, char **argv) {
   DialectRegistry registry;
   registerAllDialects(registry);
+#ifdef MLIR_INCLUDE_TESTS
+  ::test::registerTestDialect(registry);
+  ::test::registerTestTransformDialectExtension(registry);
+#endif
   return failed(MlirLspServerMain(argc, argv, registry));
 }