ADD: Add and rename symbology types

Author: cjdsellers

include/databento/enums.hpp

@@ -70,9 +70,9 @@ enum SType : std::uint8_t {
   // "parent" symbol, e.g. ES.FUT to refer to all ES futures.
   Parent = 4,
   // Symbology for US equities using NASDAQ Integrated suffix conventions.
-  Nasdaq = 5,
+  NasdaqSymbol = 5,
   // Symbology for US equities using CMS suffix conventions.
-  Cms = 6,
+  CmsSymbol = 6,
 };
 }  // namespace stype
 using SType = stype::SType;