[feat] Add serve

[tchaton]

What does this PR do?

This PR add serve functionalities to Flash.

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[pep8speaks]

Hello @tchaton! Thanks for updating this PR.

• In the file flash/core/serve/dag/optimization.py:

Line 702:25: W503 line break before binary operator
Line 703:25: W503 line break before binary operator
Line 878:13: W503 line break before binary operator

Comment last updated at 2021-06-11 16:52:58 UTC

[codecov]

Codecov Report

Merging #399 (e39293c) into master (5552a78) will decrease coverage by 5.04%.
The diff coverage is 76.48%.

@@            Coverage Diff             @@
##           master     #399      +/-   ##
==========================================
- Coverage   89.82%   84.78%   -5.05%     
==========================================
  Files          80      109      +29     
  Lines        4217     6591    +2374     
==========================================
+ Hits         3788     5588    +1800     
- Misses        429     1003     +574     

Flag	Coverage Δ
unittests	84.78% <76.48%> (-5.05%)	⬇️

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

Impacted Files	Coverage Δ
flash/core/serve/dag/visualize.py	20.93% <20.93%> (ø)
flash/__init__.py	88.88% <33.33%> (-11.12%)	⬇️
flash/core/serve/interfaces/http.py	40.50% <40.50%> (ø)
flash/core/serve/core.py	41.35% <41.35%> (ø)
flash/core/serve/execution.py	41.72% <41.72%> (ø)
flash/core/serve/composition.py	43.66% <43.66%> (ø)
flash/core/serve/utils.py	44.82% <44.82%> (ø)
flash/core/serve/interfaces/models.py	45.58% <45.58%> (ø)
flash/core/model.py	80.68% <46.42%> (-6.86%)	⬇️
flash/core/data/process.py	85.20% <57.69%> (-3.64%)	⬇️
... and 64 more

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[luiscape]

The major change I suggest is on the naming of FlashServeModel to just Serve. It's more elegant and in-line with other project naming conventions, i.e. Task.