expression: check decimal scale and precision before casting

[amyangfei]

What problem does this PR solve?

part of #11223 fix issue #11193

What is changed and how it works?

Check the Flen of a record is not greater than mysql.MaxDecimalWidth and the Decimal of a record is not greater than mysql.MaxDecimalScale before casting to a decimal.

Check List

Tests

• Unit test
• Integration test

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

[codecov]

Codecov Report

Merging #11644 into master will decrease coverage by 0.5056%.
The diff coverage is 100%.

@@               Coverage Diff                @@
##             master     #11644        +/-   ##
================================================
- Coverage   81.7785%   81.2729%   -0.5057%     
================================================
  Files           426        426                
  Lines         94345      92006      -2339     
================================================
- Hits          77154      74776      -2378     
- Misses        11788      11858        +70     
+ Partials       5403       5372        -31

[amyangfei]

/run-all-tests

[amyangfei]

some sqllogic test case failed, like
[2019-08-06T15:13:21.926Z] 2019/08/06 23:13:21.670 main.go:137: [error] /git/sqllogictest/test/random/expr/slt_good_117.test:34457: query err Error 1426: Too big precision 66 specified for column '72'. Maximum is 65. - sql[ SELECT ALL 91 + - CASE 40 WHEN ( - 72 ) THEN + 67 ELSE - SUM( DISTINCT - 72 ) END ]
will investigate it later