sqlparse: TokenList.__init__ materializes O(subtree) value per group, causing CPU DoS before depth/token caps trigger

Summary sqlparse ships hard limits MAXGROUPINGDEPTH=100, MAXGROUPINGTOKENS=10000 intended to bound parsing work on attacker-supplied SQL, but the path that reaches those limits is itself Ondepth per token-group construction. A 1-2 KB SQL payload e.g. SELECT 1 ... with 500-2000 nesting levels, or ...