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/Feature_test.cpp

@@ -347,9 +347,12 @@ class Feature_test : public beast::unit_test::suite
                 (*it).isMember(jss::enabled) && (*it)[jss::enabled].asBool() == expectEnabled,
                 (*it)[jss::name].asString() + " enabled");
             if (expectEnabled)
+            {
                 BEAST_EXPECTS(
                     !(*it).isMember(jss::vetoed), (*it)[jss::name].asString() + " vetoed");
+            }
             else
+            {
                 BEAST_EXPECTS(
                     (*it).isMember(jss::vetoed) && (*it)[jss::vetoed].isBool() == !expectObsolete &&
                         (!(*it)[jss::vetoed].isBool() ||
@@ -357,6 +360,7 @@ class Feature_test : public beast::unit_test::suite
                         ((*it)[jss::vetoed].isBool() ||
                          (*it)[jss::vetoed].asString() == "Obsolete"),
                     (*it)[jss::name].asString() + " vetoed");
+            }
             BEAST_EXPECTS(
                 (*it).isMember(jss::supported) && (*it)[jss::supported].asBool() == expectSupported,
                 (*it)[jss::name].asString() + " supported");