refactor: move package dfget/util to pkg/algorithm

[lowzj]

Signed-off-by: lowzj [email protected]

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)? (你真的觉得不需要加测试吗？)

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #1318 into master will decrease coverage by 0.00%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #1318      +/-   ##
==========================================
- Coverage   51.16%   51.16%   -0.01%     
==========================================
  Files         124      123       -1     
  Lines        8175     8177       +2     
==========================================
+ Hits         4183     4184       +1     
  Misses       3654     3654              
- Partials      338      339       +1     

Impacted Files	Coverage Δ
cmd/dfdaemon/app/init.go	0.00% <0.00%> (ø)
pkg/algorithm/algorithm.go	80.85% <67.85%> (-19.15%)	⬇️
dfget/core/core.go	45.78% <100.00%> (ø)
supernode/daemon/mgr/scheduler/manager.go	21.91% <0.00%> (-0.69%)	⬇️

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[starnop]

LGTM.