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/libxrpl/protocol/Serializer.cpp

@@ -112,8 +112,10 @@ Serializer::addFieldID(int type, int name)
 
     if (type < 16)
     {
-        if (name < 16)  // common type, common name
+        if (name < 16)
+        {  // common type, common name
             mData.push_back(static_cast<unsigned char>((type << 4) | name));
+        }
         else
         {
             // common type, uncommon name
@@ -187,7 +189,7 @@ int
 Serializer::addVL(Slice const& slice)
 {
     int ret = addEncoded(slice.size());
-    if (slice.size())
+    if (!slice.empty())
         addRaw(slice.data(), slice.size());
     return ret;
 }
@@ -230,7 +232,9 @@ Serializer::addEncoded(int length)
         numBytes = 3;
     }
     else
+    {
         Throw<std::overflow_error>("lenlen");
+    }
 
     return addRaw(&bytes[0], numBytes);
 }