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/consensus/LedgerTiming_test.cpp

@@ -29,11 +29,17 @@ class LedgerTiming_test : public beast::unit_test::suite
                     nextCloseResolution =
                         getNextLedgerTimeResolution(closeResolution, previousAgree, ++round);
                     if (nextCloseResolution < closeResolution)
+                    {
                         ++res.decrease;
+                    }
                     else if (nextCloseResolution > closeResolution)
+                    {
                         ++res.increase;
+                    }
                     else
+                    {
                         ++res.equal;
+                    }
                     std::swap(nextCloseResolution, closeResolution);
                 } while (round < rounds);
                 return res;