planner/core: fix the 'for update' condition for the point get query

[tiancaiamao]

What problem does this PR solve?

Fix bug introduced in #11715

Sometimes, InTxn() is not precise, so we should check both InTxn() and autocommit

// We should set the 'for update' flag in this case.
set @@auto_commit = 0;
select * from t where id = 6 for update;  // This is not InTxn() when the planner run here, because it's still in the plan phase.

What is changed and how it works?

The check condition is changed from InTxn() to IsAutocommit() || InTxn()

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

Related changes

• Need to cherry-pick to the release branch

[codecov]

Codecov Report

Merging #11771 into master will decrease coverage by 0.0212%.
The diff coverage is 100%.

@@               Coverage Diff               @@
##            master     #11771        +/-   ##
===============================================
- Coverage   81.478%   81.4567%   -0.0213%     
===============================================
  Files          434        434                
  Lines        93381      93274       -107     
===============================================
- Hits         76085      75978       -107     
- Misses       11858      11869        +11     
+ Partials      5438       5427        -11

[codecov]

Codecov Report

Merging #11771 into master will decrease coverage by 0.2305%.
The diff coverage is 100%.

@@               Coverage Diff                @@
##             master     #11771        +/-   ##
================================================
- Coverage   81.6663%   81.4358%   -0.2306%     
================================================
  Files           435        434         -1     
  Lines         93964      93368       -596     
================================================
- Hits          76737      76035       -702     
- Misses        11789      11891       +102     
- Partials       5438       5442         +4

[jackysp]

LGTM

[coocood]

LGTM

[sre-bot]

/run-all-tests

[sre-bot]

cherry pick to release-3.0 in PR #11775