Feature/add chain id to stats

[CodeWarriorr]

Changelog

Enhancements

Added Chain ID to /api/v2/stats

Checklist for your Pull Request (PR)

• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to docs repository.
• If I added/changed/removed ENV var, I submitted a PR to docs repository to update the list of env vars and I updated the version to master in the Version column. If I removed variable, I added it to Deprecated ENV Variables page. After merging docs PR, changes will be reflected in these pages.
• If I added new DB indices, I checked, that they are not redundant, with PGHero or other tools.
• If I added/removed chain type, I modified the Github CI matrix and PR labels accordingly.