feat(nexus): add sampled history

[kptkin]

Description

• Fixes WB-NNNNN
• Fixes #NNNN

What does the PR do?

🤖 Generated by Copilot at 3626270

This pull request adds a sampled history feature to the nexus service, which allows clients to query a random subset of history records for a given key. It implements a reservoir sampling algorithm in the ReservoirSampling type and the sampleHistory method, and exposes a new endpoint in the handleSampledHistory method in the handler.go file.

Testing

How was this PR tested?

🤖 Generated by Copilot at 3626270

To query the nexus service faster
We added a new field and method
The ReservoirSampling type
Uses a clever algorithmic hype
To store and return a sampled history master

[codecov]

Codecov Report

Merging #6492 (3626270) into main (e7ec02b) will decrease coverage by 0.14%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6492      +/-   ##
==========================================
- Coverage   77.22%   77.08%   -0.14%     
==========================================
  Files         387      387              
  Lines       44928    45007      +79     
==========================================
- Hits        34694    34693       -1     
- Misses      10181    10261      +80     
  Partials       53       53              

Flag	Coverage Δ
unittest	81.21% <ø> (-0.01%)	⬇️

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

Files	Coverage Δ
nexus/pkg/server/handler.go	0.00% <0.00%> (ø)
nexus/pkg/server/history.go	0.00% <0.00%> (ø)

... and 21 files with indirect coverage changes