Add changelog for v0.16.0

[adchia]

What this PR does / why we need it:
Adds the changelog for v0.16.0

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[achals]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: achals, adchia

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[codecov-commenter]

Codecov Report

Merging #2120 (466a546) into master (5ab6232) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2120      +/-   ##
==========================================
- Coverage   57.99%   57.98%   -0.02%     
==========================================
  Files         100      100              
  Lines        8088     8088              
==========================================
- Hits         4691     4690       -1     
- Misses       3397     3398       +1     

Flag	Coverage Δ
unittests	57.98% <ø> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
sdk/python/tests/conftest.py	61.79% <0.00%> (-1.13%)	⬇️

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