Upgrade stable Rust to 1.52 version

[alexlapa]

Synopsis

Rust v1.52 is out, let's upgrade.

Checklist

• Created PR:
  • [x] In draft mode
  • [x] Name contains Draft: prefix
  • [x] Name contains issue reference
  • [x] Has k:: labels applied
  • [x] Has assignee
• [x] Documentation is updated (if required)
• [x] Tests are updated (if required)
• [x] Changes conform code style
• [x] CHANGELOG entry is added (if required)
• [x] FCM (final commit message) is posted
  • [x] and approved
• [x] Review is completed and changes are approved
• Before merge:
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  • [x] Draft: prefix is removed
  • [x] All temporary labels are removed

[alexlapa]

FMC:

Upgrade stable Rust to 1.52 version (#199)

- update and upgrade outdated Cargo deps
- upgrade to 'tokio' 1.0 and 'actix-web' 4.0 ecosystem
- make Clippy happy with new lints
- satisfy rustdoc::private_intra_doc_links lint

Additionally:
- upgrade Chrome to 90.0 version for E2E tests
- upgrade Firefox to 88.0.1 version for E2E tests