Enable support for multiple Set-Cookie response headers (native & wsgi/asgi)

[YunchuWang]

Description

TODO:

1. Add asgi/wsgi tests

Fixes Azure/azure-functions-python-library#107

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PR information

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• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
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• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

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[codecov]

Codecov Report

Merging #1004 (e845986) into dev (1b52d72) will increase coverage by 0.55%.
The diff coverage is 96.25%.

@@            Coverage Diff             @@
##              dev    #1004      +/-   ##
==========================================
+ Coverage   83.46%   84.01%   +0.55%     
==========================================
  Files          33       34       +1     
  Lines        1778     1858      +80     
  Branches      282      299      +17     
==========================================
+ Hits         1484     1561      +77     
- Misses        230      232       +2     
- Partials       64       65       +1     

Flag	Coverage Δ
unittests	84.01% <96.25%> (+0.55%)	⬆️

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Impacted Files	Coverage Δ
azure_functions_worker/dispatcher.py	89.12% <ø> (ø)
azure_functions_worker/bindings/datumdef.py	72.22% <92.85%> (+8.49%)	⬆️
...e_functions_worker/bindings/nullable_converters.py	100.00% <100.00%> (ø)
azure_functions_worker/protos/__init__.py	100.00% <100.00%> (ø)

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