refactor: remove function pg_sleep

[fuyufjh]

What's changed and what's your intention?

We currently use std::thread::sleep to implement pg_sleep, which will put the current thread to sleep. This may block other coroutines from running and reduce system throughput.

See also #2561 (comment)

Checklist

N/A

Refer to a related PR or issue link (optional)

closes #2561

[codecov]

Codecov Report

Merging #2576 (42f292d) into main (6fd6403) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2576      +/-   ##
==========================================
- Coverage   72.16%   72.15%   -0.01%     
==========================================
  Files         675      674       -1     
  Lines       88016    87971      -45     
==========================================
- Hits        63516    63475      -41     
+ Misses      24500    24496       -4     

Flag	Coverage Δ
rust	72.15% <100.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
src/expr/src/expr/expr_unary.rs	75.97% <ø> (+0.24%)	⬆️
src/expr/src/expr/mod.rs	47.61% <100.00%> (ø)
src/common/src/types/mod.rs	65.11% <0.00%> (-0.39%)	⬇️
src/meta/src/stream/stream_manager.rs	64.02% <0.00%> (+0.14%)	⬆️

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