Add search by full text when using Oracle23ai as vector DB (#6559)

docker/startupscripts/init_user.script

@@ -0,0 +1,10 @@
+show pdbs;
+ALTER SYSTEM SET PROCESSES=500 SCOPE=SPFILE; 
+alter session set container= freepdb1;
+create user dify identified by dify DEFAULT TABLESPACE users quota unlimited on users;
+grant DB_DEVELOPER_ROLE to dify;
+
+BEGIN
+CTX_DDL.CREATE_PREFERENCE('my_chinese_vgram_lexer','CHINESE_VGRAM_LEXER');
+END;
+/