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/jtx/impl/flags.cpp

@@ -24,11 +24,17 @@ flags::operator()(Env& env) const
 {
     auto const sle = env.le(account_);
     if (!sle)
+    {
         env.test.fail();
+    }
     else if (sle->isFieldPresent(sfFlags))
+    {
         env.test.expect((sle->getFieldU32(sfFlags) & mask_) == mask_);
+    }
     else
+    {
         env.test.expect(mask_ == 0);
+    }
 }
 
 void
@@ -36,11 +42,17 @@ nflags::operator()(Env& env) const
 {
     auto const sle = env.le(account_);
     if (!sle)
+    {
         env.test.fail();
+    }
     else if (sle->isFieldPresent(sfFlags))
+    {
         env.test.expect((sle->getFieldU32(sfFlags) & mask_) == 0);
+    }
     else
+    {
         env.test.pass();
+    }
 }
 
 }  // namespace jtx