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/DepositAuth_test.cpp

@@ -1283,8 +1283,10 @@ struct DepositPreauth_test : public beast::unit_test::suite
                     auto issuer = c[jss::Issuer].asString();
 
                     if (BEAST_EXPECT(pubKey2Acc.contains(issuer)))
+                    {
                         readCreds.emplace_back(
                             pubKey2Acc.at(issuer), c["CredentialType"].asString());
+                    }
                 }
 
                 BEAST_EXPECT(std::ranges::is_sorted(readCreds));