refactor: implement version as built-in function and use fixed mysql version (#3133)

* refactor:  implement version as built-in function

* test: add sqlness test for version()

tests/cases/standalone/common/function/system.sql

@@ -5,3 +5,6 @@
 -- SQLNESS REPLACE version:\s+.+ version: VERSION
 -- SQLNESS REPLACE [\s\-]+
 SELECT build();
+
+-- SQLNESS REPLACE greptimedb-[\d\.]+ greptimedb-VERSION
+SELECT version();