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/Transaction_test.cpp

@@ -92,9 +92,13 @@ class Transaction_test : public beast::unit_test::suite
                 result[jss::result][jss::error] == NOT_FOUND);
 
             if (deltaEndSeq)
+            {
                 BEAST_EXPECT(!result[jss::result][jss::searched_all].asBool());
+            }
             else
+            {
                 BEAST_EXPECT(result[jss::result][jss::searched_all].asBool());
+            }
         }
 
         // Find transactions outside of provided range.
@@ -329,9 +333,13 @@ class Transaction_test : public beast::unit_test::suite
                 result[jss::result][jss::error] == NOT_FOUND);
 
             if (deltaEndSeq)
+            {
                 BEAST_EXPECT(!result[jss::result][jss::searched_all].asBool());
+            }
             else
+            {
                 BEAST_EXPECT(!result[jss::result][jss::searched_all].asBool());
+            }
         }
 
         // Find transactions outside of provided range.