chore: Reduce syscalls in metrics update logic

[andygrove]

Which issue does this PR close?

Closes #.

Rationale for this change

Reduce syscalls by 99% when checking whether it is time to update metrics (check once per 100 polls instead of on every poll).

What changes are included in this PR?

How are these changes tested?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.61%. Comparing base (f09f8af) to head (b37eb95).
⚠️ Report is 779 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2940      +/-   ##
============================================
+ Coverage     56.12%   59.61%   +3.48%     
- Complexity      976     1379     +403     
============================================
  Files           119      167      +48     
  Lines         11743    15430    +3687     
  Branches       2251     2550     +299     
============================================
+ Hits           6591     9198    +2607     
- Misses         4012     4946     +934     
- Partials       1140     1286     +146     

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[mbutrovich]

I suspect poll iterations will still be quick, right? We don't have to worry too much about super slow iterations delaying metrics updates? Thanks @andygrove!

[andygrove]

I suspect poll iterations will still be quick, right? We don't have to worry too much about super slow iterations delaying metrics updates? Thanks @andygrove!

The worst case is that the UI updates infrequently during execution, but the final metrics will always be updated.

[hsiang-c]

LGTM