test: E2E download concurrency

[gaius-qi]

Description

• E2E download concurrency.

Related Issue

Fixes #470

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 #467 (fe4c6b9) into main (440f888) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #467      +/-   ##
==========================================
+ Coverage   36.45%   36.49%   +0.04%     
==========================================
  Files          86       89       +3     
  Lines        6869     6959      +90     
==========================================
+ Hits         2504     2540      +36     
- Misses       4001     4051      +50     
- Partials      364      368       +4     

Flag	Coverage Δ
e2etests	∅ <ø> (?)
unittests	36.49% <ø> (+0.04%)	⬆️

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

Impacted Files	Coverage Δ
client/daemon/peer/peertask_base.go	32.21% <0.00%> (-1.20%)	⬇️
manager/searcher/search.go	82.05% <0.00%> (ø)
manager/searcher/plugin.go	50.00% <0.00%> (ø)
manager/config/config.go	0.00% <0.00%> (ø)
client/daemon/peer/peertask_stream.go	56.98% <0.00%> (+2.20%)	⬆️