Errors and warnings must be shown as separate entries in Burza reports

Currently warnings and errors are saved into the report tree, but are not shown in the reports. We'll need to show them as a separate report if such nodes exist.

Example:
https://mdbe-buildbot.mariadb.net/?#/builders/710/builds/636/steps/232/logs/stdio

[0m 2025-03-18 23:37:01,155[I] - run_progress - Running test case tpc_h:q21 (21/21)
[0m 2025-03-18 23:37:39,706[I] - run_progress - Case run tpc_h:q21[0] failed with exception: Internal error: (337) MCS-2001: Join or subselect exceeds memory limit.
[0m 2025-03-18 23:38:06,862[I] - run_progress - Case run tpc_h:q21[1] failed with exception: Internal error: (337) MCS-2001: Join or subselect exceeds memory limit.
[0m 2025-03-18 23:39:28,686[I] - run_progress - Case run tpc_h:q21[2] failed with exception: Internal error: (337) MCS-2001: Join or subselect exceeds memory limit.
[0m 2025-03-18 23:39:30,406[W] - seq_test_runner - Stopping the test case q21 due to too many exceptions (3)

We have log entries about exceeding memory limit, so the run durations report was not generated, but these errors were shown only in the logs.
The same applies to the stddev warnings.

Also these warnings/errors must get in the comparison report.