fix(metrics): use iter_in_process_count to replace iter_count_duration

[Li0k]

fix(metrics): use iter_in_process_count to replace iter_count of histogram duration

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What's changed and what's your intention?

as title

Checklist

• [ ] I have written necessary rustdoc comments
• [ ] I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

[codecov]

Codecov Report

Merging #3678 (37fb8ab) into main (a75258e) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3678      +/-   ##
==========================================
- Coverage   74.30%   74.30%   -0.01%     
==========================================
  Files         789      789              
  Lines      111361   111361              
==========================================
- Hits        82747    82742       -5     
- Misses      28614    28619       +5     

Flag	Coverage Δ
rust	74.30% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/meta/src/manager/id.rs	94.94% <0.00%> (-1.13%)	⬇️
src/connector/src/filesystem/file_common.rs	80.35% <0.00%> (-0.45%)	⬇️
src/frontend/src/expr/utils.rs	98.99% <0.00%> (-0.26%)	⬇️
src/common/src/types/ordered_float.rs	24.70% <0.00%> (-0.20%)	⬇️

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