fix: make Node microbenches more stable

[cheb0]

Description

Use const seed and call ResetTimer. They false report degradation too often, but it's possible to slow down on them actually.

---

• I have read and followed all requirements in CONTRIBUTING.md;
• I used LLM/AI assistance to make this pull request;

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.48%. Comparing base (ad03474) to head (e0b2a32).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #376      +/-   ##
==========================================
+ Coverage   71.42%   71.48%   +0.05%     
==========================================
  Files         205      206       +1     
  Lines       14910    15057     +147     
==========================================
+ Hits        10650    10764     +114     
- Misses       3484     3504      +20     
- Partials      776      789      +13     

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[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
AggDeep/size=1000-4	ad0347	96051b
	4737.00 ns/op	5498.00 ns/op	1.16	🔴
AggDeep/size=10000-4	ad0347	96051b
	47818.00 ns/op	56106.00 ns/op	1.17	🔴
AggWide/size=1000-4	ad0347	96051b
	4780.00 ns/op	5920.00 ns/op	1.24	🔴
FindSequence_Random/medium-4	ad0347	96051b
	12292.95 MB/s	11074.57 MB/s	0.90	🔴

[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
AggDeep/size=10000-4	03387c	7bc28e
	45145.00 ns/op	55798.00 ns/op	1.24	🔴
And/size=1000-4	03387c	7bc28e
	4.29 ns/op	4.82 ns/op	1.12	🔴