feat: scheduler channel blocking

[gaius-qi]

Description

• Scheduler channel blocking.

Related Issue

Fixes #749

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.

[244372610]

这里放在下一次调度，如果对应的conn已经关闭，再次send还是会有问题

[codecov-commenter]

Codecov Report

Merging #756 (3f568e6) into main (8f72ca8) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #756      +/-   ##
==========================================
+ Coverage   38.34%   38.39%   +0.04%     
==========================================
  Files          91       91              
  Lines        7033     7033              
==========================================
+ Hits         2697     2700       +3     
+ Misses       3953     3952       -1     
+ Partials      383      381       -2     

Flag	Coverage Δ
Object-compatibility-e2etests	?
e2etests	?
unittests	38.39% <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_stream.go	54.92% <0.00%> (+0.31%)	⬆️
client/daemon/peer/piece_manager.go	68.89% <0.00%> (+0.78%)	⬆️