Allows registering of features in request data as RequestFeatureView. Refactors common logic into a BaseFeatureView class

[adchia]

What this PR does / why we need it:
Introduces a new kind of feature view called RequestFeatureView, which allows for discovery of features available only at request time. This refactors common logic of feature views into a BaseFeatureView class

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

Allows registering of request data as a feature view via RequestFeatureView

[codecov-commenter]

Codecov Report

Merging #1931 (c64a452) into master (0212728) will decrease coverage by 2.08%.
The diff coverage is 81.15%.

@@            Coverage Diff             @@
##           master    #1931      +/-   ##
==========================================
- Coverage   82.26%   80.17%   -2.09%     
==========================================
  Files          96       99       +3     
  Lines        7669     8158     +489     
==========================================
+ Hits         6309     6541     +232     
- Misses       1360     1617     +257     

Flag	Coverage Δ
integrationtests	74.29% <81.84%> (+0.14%)	⬆️
unittests	59.57% <53.41%> (+0.17%)	⬆️

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

Impacted Files	Coverage Δ
sdk/python/feast/errors.py	70.00% <ø> (ø)
...python/feast/infra/offline_stores/offline_store.py	87.50% <ø> (ø)
...ts/integration/feature_repos/repo_configuration.py	93.18% <ø> (-6.82%)	⬇️
sdk/python/feast/cli.py	38.51% <16.66%> (-0.19%)	⬇️
sdk/python/feast/repo_operations.py	43.82% <25.00%> (-0.40%)	⬇️
...fline_store/test_universal_historical_retrieval.py	65.10% <66.66%> (-34.18%)	⬇️
sdk/python/feast/base_feature_view.py	77.77% <77.77%> (ø)
sdk/python/feast/registry.py	80.43% <80.00%> (-0.63%)	⬇️
sdk/python/feast/feature_store.py	91.34% <88.57%> (-3.21%)	⬇️
sdk/python/feast/feature_service.py	81.15% <100.00%> (+0.27%)	⬆️
... and 27 more

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[achals]

/lgtm

super nitty commends

[feast-ci-bot]

New changes are detected. LGTM label has been removed.

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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