Support Oracle Associate Array(Index-By table) in PL/SQL declaration

[ZhengguanLi]

Now we only support in the CREATE TYPE sql for Oracle index-by table syntax

dbtype: Oracle
dbversion: 19
druid verion: 1.2.23-SNAPSHOT
error sql:

set SERVEROUTPUT ON;

DECLARE
  TYPE population IS TABLE OF NUMBER INDEX BY VARCHAR2(64);          
  
  city_population  population;      
  i  VARCHAR2(64);                  
  
BEGIN
  city_population('Smallville')  := 2000;
  city_population('Midland')     := 750000;
  city_population('Megalopolis') := 1000000;
 
  city_population('Smallville') := 2001;
 
  i := city_population.FIRST;
 
  WHILE i IS NOT NULL LOOP
    DBMS_Output.PUT_LINE
      ('Population of ' || i || ' is ' || city_population(i));
    i := city_population.NEXT(i);
  END LOOP;
END;

testcase code:
stacktrace info:
error info: com.alibaba.druid.sql.parser.ParserException: syntax error, error in :'_tab AS TABLE OF VARCHAR2(30) INDEX', expect IS, actual AS, pos 32, line 2, column 22, token AS