Optimize for timer timeout extension

[notgull]

@cmeissl The CI issues are fixed on master, please rebase

[notgull]

@cmeissl try again

[cmeissl]

@cmeissl try again

The CI failed because the version (latest) of criterion depends on clap which requires a newer MSRV. I downgraded criterion for now, but maybe it would also be an option to split the tests and the MSRV checks in the future.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.92%. Comparing base (9558927) to head (24a4544).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #184 +/- ## ========================================== + Coverage 85.63% 85.92% +0.28% ========================================== Files 13 14 +1 Lines 1852 1989 +137 ========================================== + Hits 1586 1709 +123 - Misses 266 280 +14 ``` | [Flag](https://app.codecov.io/gh/Smithay/calloop/pull/184/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Smithay) | Coverage Δ | | |---|---|---| | [ubuntu-latest](https://app.codecov.io/gh/Smithay/calloop/pull/184/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Smithay) | `85.92% <100.00%> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Smithay#carryforward-flags-in-the-pull-request-comment) to find out more.

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[cmeissl]

@notgull I had to downgrade a few other deps, but the CI is now green finally!