refactor(types): move extract embeddings and contents into docset

[hanxiao]

Note: __str__ and __repr__ on Jina types are out of scope of this PR

[codecov]

Codecov Report

Merging #1387 (ea1acae) into master (b598437) will increase coverage by 0.15%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1387      +/-   ##
==========================================
+ Coverage   83.43%   83.58%   +0.15%     
==========================================
  Files         103      103              
  Lines        6792     6861      +69     
==========================================
+ Hits         5667     5735      +68     
- Misses       1125     1126       +1     

Impacted Files	Coverage Δ
jina/drivers/encode.py	88.23% <100.00%> (-0.66%)	⬇️
jina/drivers/index.py	94.73% <100.00%> (-0.27%)	⬇️
jina/drivers/predict.py	89.83% <100.00%> (-0.17%)	⬇️
jina/drivers/search.py	94.64% <100.00%> (-0.10%)	⬇️
jina/types/document/helper.py	100.00% <100.00%> (ø)
jina/types/sets/document_set.py	98.71% <100.00%> (+0.47%)	⬆️
jina/peapods/grpc_asyncio.py	75.51% <0.00%> (-1.03%)	⬇️
jina/logging/profile.py	55.81% <0.00%> (-0.66%)	⬇️
jina/peapods/pod.py	83.18% <0.00%> (-0.10%)	⬇️
jina/drivers/craft.py	100.00% <0.00%> (ø)
... and 27 more

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