Add deadlocks monotonic count metric

[nenadnoveljic]

What does this PR do?

new deadlock metric based on monotonic count

Motivation

see DBM-790
the existing deadlock metric based on rate is confusing

Additional Notes

QueryExecutor API was used

Review checklist (to be `filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached
• If the PR doesn't need to be tested during QA, please add a qa/skip-qa label.

[alexandre-normand]

@nenadnoveljic : Process comment: the PR title should be formatted to be friendly to the generated changelog. You can see examples of PR titles here (but note that the [Added] or [Fixed] actually comes from the changelog label and isn't coming from the PR title).

[alexandre-normand]

Oh and it looks like CI is complaining about some formatting issues here. Otherwise, this looks good to me.

[codecov]

Codecov Report

Merging #13374 (bde62fa) into master (37ac25f) will increase coverage by 0.00%.
The diff coverage is 86.31%.

Flag	Coverage Δ
postgres	91.39% <86.31%> (+0.11%)	⬆️

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