MDEV-28849: I_S.ROUTINES don't tell that the stored function is AGGRE…

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…GATE

INFORMATION_SCHEMA.ROUTINES does not tell whether a particular storage function is aggregate or not.

The fix is to add a new field FUNCTION_KIND, which is a SET type, containing NOT_FUNCTION, SCALAR and AGGREGATE values, in I_S.ROUTINES table. NOT_FUNCTION is for procedure, package, package body, trigger and event; SCALAR for non-aggregate function; AGGREGATE for aggregate function.

• The Jira issue number for this PR is: MDEV-28849

Description

1. I_S.ROUTINES does not tell whether a particular storage function is aggregate or not.
2. After the patch is applied, I_S.ROUTINES will show a new column FUNCTION_KIND.
3. The patch just works on I_S.ROUTINES table, so, i don't think it will introduce side-effects in other parts of the server.

Release Notes

1. Information Schema ROUTINES Table will add a new column FUNCTION_KIND to tell the function type;

How can this PR be tested?

The FUNCTION_KIND supports three types: NOT_FUNCTION for procedure(and package, package body, trigger, event), SCALAR for non-aggregate function and AGGREGATE for aggregate function. So, in a test, we can create a procedure, a non-aggregate function and an aggregate function in turn and check whether their FUNCTION_KIND values meet expectations.
UPDATE: the test for I_S.ROUTINES column FUNCTION_KIND has been added in server/mysql-test/main/infortmation_schema.test

If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.

Basing the PR against the correct MariaDB version

• This is a new feature or a refactoring, and the PR is based against the main branch.
• This is a bug fix, and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.