Add Vertica source and implemented singlestore customizations

Author: inancdokurel

sqlglot/dialects/__init__.py

@@ -97,6 +97,7 @@ class Generator(Generator):
     "Teradata",
     "Trino",
     "TSQL",
+    "Vertica",
 ]
 
 MODULE_BY_DIALECT = {name: name.lower() for name in DIALECTS}