infoschema: fix case of stmt_type in statement summary (#17005)

[sre-bot]

cherry-pick #17005 to release-4.0

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What problem does this PR solve?

Problem Summary:
stmt_type was transformed to lower cases, so AlterTable was transformed to altertable, which was not readable.

What is changed and how it works?

What's Changed:
Do not transform stmt_type to lower case.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

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

mysql> truncate t;
Query OK, 0 rows affected (0.01 sec)

mysql> select stmt_type, digest_text from information_schema.statements_summary where stmt_type='TruncateTable';
+---------------+-------------+
| stmt_type     | digest_text |
+---------------+-------------+
| TruncateTable | truncate t  |
+---------------+-------------+
1 row in set (0.00 sec)

Side effects

• Breaking backward compatibility

Release note

• Change the case of field stmt_type in statement summary tables.

[sre-bot]

/run-all-tests

[AilinKid]

LGTM

[Deardrops]

LGTM

[sre-bot]

/run-all-tests

[sre-bot]

@sre-bot merge failed.