refactor: Delete unnecessary errors.go file

[felixwang9817]

What this PR does / why we need it: This PR removes the errors.go file and moves featureNameCollisionError into featurestore.go.

Which issue(s) this PR fixes:

Fixes #

[achals]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [achals,felixwang9817]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov-commenter]

Codecov Report

Merging #2392 (22c479c) into master (ae133fd) will decrease coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2392      +/-   ##
==========================================
- Coverage   84.43%   84.34%   -0.10%     
==========================================
  Files         122      122              
  Lines       10732    10732              
==========================================
- Hits         9062     9052      -10     
- Misses       1670     1680      +10     

Flag	Coverage Δ
integrationtests	74.16% <100.00%> (-0.33%)	⬇️
unittests	56.99% <100.00%> (ø)

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

Impacted Files	Coverage Δ
sdk/python/feast/feature_store.py	90.97% <100.00%> (ø)
sdk/python/feast/wait.py	58.82% <0.00%> (-35.30%)	⬇️
.../integration/online_store/test_universal_online.py	82.05% <0.00%> (-0.72%)	⬇️
sdk/python/feast/go_server.py	64.57% <0.00%> (-0.58%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ae133fd...22c479c. Read the comment docs.

[achals]

/lgtm