chore: Install dependencies into a virtualenv for gitpod

[achals]

What this PR does / why we need it:

When using prebuilds (which we are), only things in the /workspace/ directory are saved. But, by default gitpod's python environment is system-wide and installs into /home, which means that all installed dependencies are lost when the workspace actually starts.

Which issue(s) this PR fixes:

Fixes #

[codecov-commenter]

Codecov Report

Merging #2749 (2a85ee9) into master (3d2b431) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2749      +/-   ##
==========================================
- Coverage   80.27%   80.24%   -0.04%     
==========================================
  Files         169      169              
  Lines       14368    14366       -2     
==========================================
- Hits        11534    11528       -6     
- Misses       2834     2838       +4     

Flag	Coverage Δ
integrationtests	70.45% <ø> (-0.37%)	⬇️
unittests	58.73% <ø> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
setup.py	0.00% <ø> (ø)
sdk/python/tests/utils/online_read_write_test.py	93.54% <0.00%> (-6.46%)	⬇️
.../integration/online_store/test_online_retrieval.py	96.84% <0.00%> (-3.16%)	⬇️
...ython/feast/embedded_go/online_features_service.py	89.14% <0.00%> (-0.78%)	⬇️

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[pyalex]

/lgtm

[adchia]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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