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/AMMExtended_test.cpp

@@ -1971,8 +1971,10 @@ private:
                     return false;
                 Sandbox sb(&view, tapNONE);
                 for (auto const& o : flowResult.removableOffers)
+                {
                     if (auto ok = sb.peek(keylet::offer(o)))
                         offerDelete(sb, ok, flowJournal);
+                }
                 sb.apply(view);
                 return true;
             });
@@ -2633,9 +2635,13 @@ private:
         // offer, removes 999 more as unfunded, then hits the step limit.
         env(offer(alice, USD(1'000), XRP(1'000)));
         if (!features[fixAMMv1_1])
+        {
             env.require(balance(alice, STAmount{USD, UINT64_C(2'050126257867561), -15}));
+        }
         else
+        {
             env.require(balance(alice, STAmount{USD, UINT64_C(2'050125257867587), -15}));
+        }
         env.require(owners(alice, 2));
         env.require(balance(bob, USD(0)));
         env.require(owners(bob, 1'001));