uptime: remove /proc dependency

[oech3]

Closes #13292

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/truncate. tests/tail/truncate is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/cut/cut-huge-range is now being skipped but was previously passing.
Congrats! The gnu test tests/expand/bounded-memory is now passing!
Congrats! The gnu test tests/rm/many-dir-entries-vs-OOM is now passing!

[sylvestre]

i am struggling to understand the commit message when i see the diff
could you please improve the commit message? thanks

[oech3]

added commit message

[codspeed-hq]

Merging this PR will not alter performance

✅ 172 untouched benchmarks
⏩ 213 skipped benchmarks¹

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_{Comparing oech3:uptime-proc (80e9f71) with main (ef50d8b)}

Footnotes

1. 213 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩