MDEV-35701 trx_t::autoinc_locks causes unnecessary dynamic memory allocation

[dr-m]

• The Jira issue number for this PR is: MDEV-35701

Description

trx_t::autoinc_locks: Use small_vector<lock_t*,4> in order to avoid any dynamic memory allocation in the most common case (a statement is holding AUTO_INCREMENT locks on at most 4 tables or partitions).

lock_cancel_waiting_and_release(): Instead of removing elements from the middle, simply assign nullptr, like lock_table_remove_autoinc_lock().

Release Notes

This is a minor performance improvement.

How can this PR be tested?

A simple Sysbench is expected to show some impact. I did not test this yet.

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.

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