expression: remove the NotNullFlag for aggregation func MAX/MIN when inferring type (#11343)

[sre-bot]

cherry-pick #11343 to release-3.0

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What problem does this PR solve?

Fix issue #11332

What is changed and how it works?

IF scalefunc is MAX or MIN, remove not null flag.

Check List

Tests

• Unit test

[sre-bot]

/run-all-tests

[zz-jason]

LGTM

[AndrewDi]

@zz-jason Robert didn't pick newest commit...

[XuHuaiyu]

What does newest commit mean?

[AndrewDi]

@XuHuaiyu Commit #545bff7dced9862a297faf8d2f3d1e6067700b21 add following test case:

tidb/expression/integration_test.go

Line 2747 in 545bff7

tk.MustExec("create table t1(a bigint not null")

and this PR pick the code as

tidb/expression/integration_test.go

Line 2757 in d9032e3

tk.MustExec("create table t1(a bigint not null")

newest commit modify code like this:

tidb/expression/integration_test.go

Line 2747 in d5060fc

tk.MustExec("create table t1(a bigint not null)")

[CLAassistant]

All committers have signed the CLA.

[you06]

Hi @AndrewDi, update branch will submit some commits into PR's head branch, I'm afraid this makes the difference of your origin PR and this PR.

[SunRunAway]

Abandon this pr and use the traditional way git cherry-pick 829ba98. See #11641