*: fix type of maxint64

[wjhuang2016]

What problem does this PR solve?

For #9823

What is changed and how it works?

In parser:

	case n < math.MaxInt64:
		lval.item = int64(n)

In fact, we need:

	case n <= math.MaxInt64:
		lval.item = int64(n)

Check List

Tests

• Manual test (add detailed scripts or steps below)

mysql> SELECT 9223372036854775807+1;
ERROR 1690 (22003): BIGINT value is out of range in '(9223372036854775807 + 1)'

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

[eurekaka]

Add the link of PR in parser here for reference: pingcap/parser#251

[crazycs520]

LGTM, Please update go.mod.

[codecov]

Codecov Report

Merging #9834 into master will increase coverage by 0.0099%.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             master      #9834        +/-   ##
================================================
+ Coverage   67.3446%   67.3545%   +0.0099%     
================================================
  Files           383        383                
  Lines         80437      80437                
================================================
+ Hits          54170      54178         +8     
+ Misses        21421      21417         -4     
+ Partials       4846       4842         -4

[winoros]

lgtm

[eurekaka]

LGTM

[eurekaka]

/run-all-tests

[zz-jason]

/run-unit-test