Decimal(a,b) cast to Decimal(b,c) is forbidden

[EmmyMiao87]

Describe the bug
mysql> select cast(k5 as decimal(15,4)) from baseall;
ERROR 1064 (HY000): Invalid type cast of k5 from DECIMAL(9,0) to DECIMAL(15,4)

To Reproduce
Steps to reproduce the behavior:
1.

CREATE TABLE `baseall` (
  `k1` tinyint(4) NOT NULL COMMENT "",
  `k2` smallint(6) NOT NULL COMMENT "",
  `k3` int(11) NOT NULL COMMENT "",
  `k4` bigint(20) NOT NULL COMMENT "",
  `k5` decimal(9, 3) NOT NULL COMMENT "",
  `k6` char(5) NOT NULL COMMENT "",
  `k10` date NOT NULL COMMENT "",
  `k11` datetime NOT NULL COMMENT "",
  `k7` varchar(20) NOT NULL COMMENT "",
  `k8` double MAX NOT NULL COMMENT "",
  `k9` float SUM NOT NULL COMMENT ""
) ENGINE=OLAP
AGGREGATE KEY(`k1`, `k2`, `k3`, `k4`, `k5`, `k6`, `k10`, `k11`, `k7`)
COMMENT "OLAP"
DISTRIBUTED BY HASH(`k1`) BUCKETS 5
PROPERTIES (
"storage_type" = "COLUMN"
);

2. mysql> select cast(k5 as decimal(15,4)) from baseall;

Expected behavior
return the value of k5 in baseall;

The tpc-ds query 18,61 are the same error as above.

[EmmyMiao87]

In fact, Doris does not check the precision of decimal in query. So the precision and scale in decimalV2 is useless during query.

[EmmyMiao87]

#2131