fix: add MarkCacheBytes to SystemMetrics query mapping

[Victor-Davidescu]

What does this PR do?

Adds MarkCacheBytes to the SystemMetrics query mapping so that the clickhouse.table.mergetree.storage.mark.cache metric is collected for users running ClickHouse 25.x+.

The existing entry in SystemAsynchronousMetrics is kept for backwards compatibility with older ClickHouse versions. Only one table will ever contain the metric, so there's no risk of double-reporting.

Motivation

ClickHouse PR #81023 (merged June 2025) moved MarkCacheBytes from system.asynchronous_metrics to system.metrics. As a result, the clickhouse.table.mergetree.storage.mark.cache metric is no longer collected for users running ClickHouse 25.x+.

Verified against ClickHouse 25.12.3.21:

• SELECT metric FROM system.asynchronous_metrics WHERE metric = 'MarkCacheBytes' → 0 rows
• SELECT metric FROM system.metrics WHERE metric = 'MarkCacheBytes' → 1 row

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.11%. Comparing base (4613486) to head (050d606).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

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