refactor: Add simple clang-tidy readability checks (#6556)

This change enables the following clang-tidy checks:
-  readability-avoid-nested-conditional-operator,
-  readability-avoid-return-with-void-value,
-  readability-braces-around-statements,
-  readability-const-return-type,
-  readability-container-contains,
-  readability-container-size-empty,
-  readability-else-after-return,
-  readability-make-member-function-const,
-  readability-redundant-casting,
-  readability-redundant-inline-specifier,
-  readability-redundant-member-init,
-  readability-redundant-string-init,
-  readability-reference-to-constructed-temporary,
-  readability-static-definition

src/libxrpl/ledger/ApplyStateTable.cpp

@@ -169,9 +169,11 @@ ApplyStateTable::apply(
                     "xrpl::detail::ApplyStateTable::apply : valid nodes for "
                     "modification");
 
-                if (curNode->isThreadedType(to.rules()))  // thread transaction to node
-                                                          // item modified
+                if (curNode->isThreadedType(to.rules()))
+                {  // thread transaction to node
+                   // item modified
                     threadItem(meta, curNode);
+                }
 
                 STObject prevs(sfPreviousFields);
                 for (auto const& obj : *origNode)