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/ValidatorSite_test.cpp

@@ -225,8 +225,10 @@ private:
 
             Json::Value myStatus;
             for (auto const& vs : jv[jss::validator_sites])
+            {
                 if (vs[jss::uri].asString().find(u.uri) != std::string::npos)
                     myStatus = vs;
+            }
             BEAST_EXPECTS(
                 myStatus[jss::last_refresh_message].asString().empty() != u.cfg.failFetch,
                 to_string(myStatus) + "\n" + sink.messages().str());
@@ -307,8 +309,10 @@ private:
             auto const jv = sites->getJson();
             Json::Value myStatus;
             for (auto const& vs : jv[jss::validator_sites])
+            {
                 if (vs[jss::uri].asString().find(u.uri) != std::string::npos)
                     myStatus = vs;
+            }
             BEAST_EXPECTS(
                 myStatus[jss::last_refresh_message].asString().empty() != u.shouldFail,
                 to_string(myStatus));