fix(wasi): date clock resolution and system datetime support

[eduardomourar]

date implements get_clock_resolution via libc::clock_getres (rustix's excludes WASI) and set_system_datetime for WASI, the latter reporting "not supported" since the sandbox has no wall-clock-set syscall.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/printf/printf-surprise is now passing!
Note: The gnu test tests/misc/write-errors was skipped on 'main' but is now failing.

[codspeed-hq]

Merging this PR will not alter performance

✅ 10 untouched benchmarks
⏩ 408 skipped benchmarks¹

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_{Comparing eduardomourar:wasi-date-fixes (7cc713f) with main (13deb96)²}

Footnotes

1. 408 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. ↩

2. No successful run was found on main (6cdc202) during the generation of this report, so 13deb96 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[eduardomourar]

@sylvestre, this one is ready (now with proper testing in place).

[github-actions]

Binary size comparison:

Individual binary size comparison VS main (threshold: >=5% AND >=4 KB).

Total size of compared binaries: 153.09 MB (+912 KB, +0.59%)

Significant per-binary changes:
  expr     2.76 MB ->    3.65 MB  (+908 KB, +32.11%)