test: refactor type sets test

[bwanglzu]

This PR do 2 things:

1. Move all chunkset, documentset, and matchset into set folder.
2. Experimentation, create an empty test_querylangset.py with pre-defined methods and docstrings, try to attract community members contribute to this piece of test. cc @alexcg1 @pswu11

The idea comes from @bio-howard :

1. Structure tests.
2. Fill docstrings.
3. Define new test cases and open good first issue tasks.

[codecov]

Codecov Report

Merging #1417 (b237d5b) into master (0094bbf) will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1417      +/-   ##
==========================================
+ Coverage   82.21%   82.30%   +0.08%     
==========================================
  Files         106      105       -1     
  Lines        7064     7060       -4     
==========================================
+ Hits         5808     5811       +3     
+ Misses       1256     1249       -7     

Impacted Files	Coverage Δ
jina/drivers/querylang/select.py	79.31% <0.00%> (-6.90%)	⬇️
jina/types/document/__init__.py	92.27% <0.00%> (ø)
jina/types/sets/__init__.py
jina/peapods/zmq.py	83.98% <0.00%> (+1.96%)	⬆️
jina/logging/sse.py	95.16% <0.00%> (+3.22%)	⬆️

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