Use thread-safe atomic in perfmon seeder
Use thread-safe atomic in perfmon seeder

Summary:
```
Also switch to chrono based types.
```

Partial backport of core [[https://github.com/bitcoin/bitcoin/pull/17270 | PR17270]]:
https://github.com/bitcoin/bitcoin/pull/17270/commits/64e1e022cedf6776c5dffd488ca2e766adca5dc3

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6208

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