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/LedgerRPC_test.cpp

@@ -30,10 +30,12 @@ class LedgerRPC_test : public beast::unit_test::suite
             BEAST_EXPECT(jv[jss::error_message] == Json::nullValue || jv[jss::error_message] == "");
         }
         else if (BEAST_EXPECT(jv.isMember(jss::error_message)))
+        {
             BEAST_EXPECTS(
                 jv[jss::error_message] == msg,
                 "Expected error message \"" + msg + "\", received \"" +
                     jv[jss::error_message].asString() + "\"");
+        }
     }
 
     // Corrupt a valid address by replacing the 10th character with '!'.
@@ -634,15 +636,19 @@ class LedgerRPC_test : public beast::unit_test::suite
             BEAST_EXPECT(jrr[jss::ledger][jss::accountState].isArray());
 
             for (auto i = 0; i < jrr[jss::ledger][jss::accountState].size(); i++)
+            {
                 if (jrr[jss::ledger][jss::accountState][i]["LedgerEntryType"] == jss::LedgerHashes)
                 {
                     index = jrr[jss::ledger][jss::accountState][i]["index"].asString();
                     hashesLedgerEntryIndex = i;
                 }
+            }
 
             for (auto const& object : jrr[jss::ledger][jss::accountState])
+            {
                 if (object["LedgerEntryType"] == jss::LedgerHashes)
                     index = object["index"].asString();
+            }
 
             // jss::type is a deprecated field
             BEAST_EXPECT(