json: do not escape html special values (#14518)

[sre-bot]

cherry-pick #14518 to release-3.0

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What problem does this PR solve?

For

create table test (data JSON);
insert into test (data) values ('{"a":"&"}');
select * from test;

MySQL would have result {"a":"&"}, while tidb shows {"a": "\u0026"}.

What is changed and how it works?

Do not escape the special html values &, > and <.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

Side effects

• None

Related changes

• Need to cherry-pick to the release branch

Release note

• do not escape html special values in json

[sre-bot]

/run-all-tests

[eurekaka]

LGTM

[zz-jason]

LGTM

[sre-bot]

Your auto merge job has been accepted, waiting for 14634, 14582

[sre-bot]

/run-all-tests