types: Fix checkMonthDay() to correctly handle leap year

[erjiaqing]

What problem does this PR solve?

1900-02-29 is not a valid date. However:

In TiDB:

mysql> insert into t1 values ("1900-02-29 00:00:00");
Query OK, 1 row affected (0.00 sec)

MySQL does not consider 1900 as a leap year. So this is not intended.

In MySQL:

mysql> insert into t1 values ("1900-02-29 00:00:00");
ERROR 1292 (22007): Incorrect datetime value: '1900-02-29 00:00:00' for column 't' at row 1

What is changed and how it works?

if month == 2 && !isLeapYear(uint16(year)) {
	maxDay = 28
}

Check List

Tests

• Unit test

[codecov]

Codecov Report

Merging #10342 into master will decrease coverage by 0.0189%.
The diff coverage is 100%.

@@               Coverage Diff               @@
##             master     #10342       +/-   ##
===============================================
- Coverage   77.6767%   77.6578%   -0.019%     
===============================================
  Files           411        411               
  Lines         85440      85390       -50     
===============================================
- Hits          66367      66312       -55     
- Misses        14112      14116        +4     
- Partials       4961       4962        +1

[codecov]

Codecov Report

Merging #10342 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@              Coverage Diff               @@
##             master     #10342      +/-   ##
==============================================
+ Coverage   77.6662%   77.6762%   +0.01%     
==============================================
  Files           411        411              
  Lines         85440      85389      -51     
==============================================
- Hits          66358      66327      -31     
+ Misses        14118      14103      -15     
+ Partials       4964       4959       -5

[zhouqiang-cl]

/rebuild

[lysu]

LGTM

[zz-jason]

LGTM

[zz-jason]

/run-all-tests

[zz-jason]

@erjiaqing please cherry pick this bug-fix to release-2.1