MDEV-16335: Include deadlock detail information in SHOW WARNINGS

[varundeepsaini]

• The Jira issue number for this PR is: MDEV-16335

Description

Currently, deadlock information is only available globally via SHOW ENGINE INNODB STATUS, so a client can never be certain that the information shown is for their own session's deadlock.

This patch stores deadlock information in the victim transaction's structure when a deadlock is detected, making it accessible via SHOW WARNINGS.

Implementation

• Added deadlock_info fields to trx_lock_t to store per-session deadlock information
• In Deadlock::report(), copy deadlock info to the victim transaction (only when srv_print_all_deadlocks is set)
• In convert_error_code_to_mysql(), push deadlock info as a warning via push_warning_printf()
• Clear deadlock info when a new transaction starts or when the transaction is freed

Release Notes

When innodb_print_all_deadlocks=ON, deadlock detail information is now available per-session via SHOW WARNINGS after a deadlock error (ER_LOCK_DEADLOCK).

How can this PR be tested?

./mtr --suite=innodb deadlock_session_info

Basing the PR against the correct MariaDB version

• This is a new feature and the PR is based against the main branch.

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.

[CLAassistant]

All committers have signed the CLA.

[FooBarrior]

We cannot read more than ftell returned: deadlock_info is a temporary file and we access it under lock.
We can put assert

ut_ad(len >= deadlock_info_len);

maybe +1 somewhere -- please check.

Then this if is not needed, as well as zero assignment.

[FooBarrior]

What we know is that fread can return only less bytes than ftell did:
https://en.cppreference.com/w/c/io/fread#:~:text=stream%20to%20read-,Return%20value,-Number%20of%20objects