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/app/RCLValidations_test.cpp

@@ -112,9 +112,13 @@ class RCLValidations_test : public beast::unit_test::suite
             for (Seq s = a.seq(); s > 0; s--)
             {
                 if (s >= a.minSeq())
+                {
                     BEAST_EXPECT(a[s] == history[s - 1]->header().hash);
+                }
                 else
+                {
                     BEAST_EXPECT(a[s] == ID{0});
+                }
             }
         }