Add a caching step to our github actions

[achals]

Signed-off-by: Achal Shah achals@gmail.com

What this PR does / why we need it:

Github has a way of caching dependencies on a per-job level, which can be used to speed up actions/builds by caching dependencies and builds.

Our dependencies don't change that often - so we can cache the step of installing and setting up our python environment.

Example:

• Before Caching: https://github.com/feast-dev/feast/runs/3773858745?check_suite_focus=true
• After Caching: https://github.com/feast-dev/feast/runs/3773917413?check_suite_focus=true

Install Dependencies went from 1m19s to 25s.

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

none

[codecov-commenter]

Codecov Report

Merging #1919 (d85c4af) into master (0155284) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1919   +/-   ##
=======================================
  Coverage   82.97%   82.97%           
=======================================
  Files          96       96           
  Lines        7376     7376           
=======================================
  Hits         6120     6120           
  Misses       1256     1256           

Flag	Coverage Δ
integrationtests	74.41% <ø> (ø)
unittests	60.64% <ø> (ø)

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

Impacted Files	Coverage Δ
sdk/python/tests/conftest.py	95.31% <ø> (ø)
sdk/python/tests/utils/online_read_write_test.py	100.00% <ø> (ø)

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[felixwang9817]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: achals, felixwang9817

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• OWNERS [achals,felixwang9817]

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