Client sessions advanced metrics

Pull Request description

Advanced client sessions statistics.

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[x] The milestone is specified and corresponds to fix version.
[x] Description references specific issue.
[x] Description contains human-readable scope of changes.
[x] Description contains brief notes about what needs to be added to the documentation.
[x] No merge conflicts, commented blocks of code, code formatting issues.
[x] Changes are backward compatible or upgrade script is provided.

[x] Screenshots with affected component(s) are added. The best option is to provide 2 screens: before and after changes;
[x] If you change the widget or other API, ensure it is backward-compatible or upgrade script is present.

[x] Added corresponding unit and/or integration test(s). Provide written explanation in the PR description if you have failed to add tests.
[x] If new dependency was added: the dependency tree is checked for conflicts.