feat: search scheduler cluster

[gaius-qi]

Description

• Add search.SchedulerCluster to choose the optimal schedulers.
• Add search plugin to provide custom search methods.

Related Issue

Fixes #456

Motivation and Context

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist:

• Code compiles correctly.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-commenter]

Codecov Report

Merging #462 (79c9c3c) into main (b2ca351) will increase coverage by 0.01%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##             main     #462      +/-   ##
==========================================
+ Coverage   36.38%   36.39%   +0.01%     
==========================================
  Files          86       89       +3     
  Lines        6869     6959      +90     
==========================================
+ Hits         2499     2533      +34     
- Misses       4005     4057      +52     
- Partials      365      369       +4     

Flag	Coverage Δ
e2etests	∅ <ø> (∅)
unittests	36.39% <77.77%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
manager/searcher/plugin.go	50.00% <50.00%> (ø)
manager/searcher/search.go	82.05% <82.05%> (ø)
client/daemon/peer/peertask_stream_callback.go	62.02% <0.00%> (-2.54%)	⬇️
manager/config/config.go	0.00% <0.00%> (ø)
client/daemon/peer/peertask_stream.go	55.14% <0.00%> (+0.36%)	⬆️