Add Local as valid type for autoscaler source

[jennchenn]

What does this PR do?

Add Local as valid type for autoscaler source.

Motivation

Implementing local fallback

Additional Notes

Anything else we should know when reviewing?

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Cluster Agent: v7.56.0

Describe your test plan

Will be tested as part of changes made to autoscaling controller for local fallback.

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.66%. Comparing base (6ff015c) to head (69f76ab).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1513   +/-   ##
=======================================
  Coverage   48.66%   48.66%           
=======================================
  Files         226      226           
  Lines       20363    20363           
=======================================
  Hits         9909     9909           
  Misses       9937     9937           
  Partials      517      517           

Flag	Coverage Δ
unittests	48.66% <ø> (ø)

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

Files with missing lines	Coverage Δ
...i/datadoghq/v1alpha1/datadogpodautoscaler_types.go	100.00% <ø> (ø)

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