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/test/rpc/DepositAuthorized_test.cpp

@@ -246,9 +246,11 @@ public:
         if (result.isMember(jss::deposit_authorized))
             BEAST_EXPECT(result[jss::deposit_authorized] == authorized);
         if (authorized)
+        {
             BEAST_EXPECT(
                 result.isMember(jss::deposit_authorized) &&
                 (result[jss::deposit_authorized] == true));
+        }
 
         BEAST_EXPECT(result.isMember(jss::error) == !error.empty());
         if (!error.empty())