feat: separate CI, lazily load heavily module

[aarnphm]

Description

• update black to 21.4b2
• separate integration framework CI
• lazily load heavy ml module
• add mypy as dependency for typeshed

Jax and GPU support will be addressed once some 1.0 features are decided

Checklist:

• My code follows the bentoml code style, both ./dev/format.sh and
  ./dev/lint.sh script have passed
  (instructions).
• My change reduces project test coverage and requires unit tests to be added
• I have added unit tests covering my code change
• My change requires a change to the documentation
• I have updated the documentation accordingly

[codecov]

Codecov Report

Merging #1829 (9e46248) into bentoml-1.0 (aab3f23) will increase coverage by 0.73%.
The diff coverage is 65.86%.

@@               Coverage Diff               @@
##           bentoml-1.0    #1829      +/-   ##
===============================================
+ Coverage        20.32%   21.05%   +0.73%     
===============================================
  Files              106      106              
  Lines             6161     6145      -16     
===============================================
+ Hits              1252     1294      +42     
+ Misses            4909     4851      -58     

Impacted Files	Coverage Δ
bentoml/__init__.py	100.00% <ø> (ø)
...entoml/_internal/adapters/annotated_image_input.py	0.00% <ø> (ø)
bentoml/_internal/adapters/base_output.py	0.00% <ø> (ø)
bentoml/_internal/adapters/dataframe_input.py	0.00% <0.00%> (ø)
bentoml/_internal/adapters/dataframe_output.py	0.00% <0.00%> (ø)
bentoml/_internal/adapters/default_output.py	0.00% <ø> (ø)
bentoml/_internal/adapters/file_input.py	0.00% <ø> (ø)
bentoml/_internal/adapters/image_input.py	0.00% <ø> (ø)
bentoml/_internal/adapters/json_output.py	0.00% <0.00%> (ø)
bentoml/_internal/adapters/multi_file_input.py	0.00% <0.00%> (ø)
... and 52 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update aab3f23...9e46248. Read the comment docs.

[parano]

do we need it here?

[aarnphm]

mainly for context managers to be type-safe. There would be a fix when we upgrade to 3.10 (using ParamSpec). This is @yetone's patch #1785

[aarnphm]

Note: We will revisit the mypy dependency once we have access to ParamSpec.