Draft: Add directories to DS_EXCLUDED_PATHS

What does this MR do?

Add three more directories to DS_EXCLUDED_PATHS:

• .git directory
• directories corresponding to test files
  • fixtures, convention for at least Ruby and Node projects
  • testdata, convention for Go projects

Skipping .git is aligned with the default behavior of the search package of the common library, used to determine whether an analyzer should run. That's because SEARCH_IGNORE_HIDDEN_DIRS is true by default.

Screenshots (strongly suggested)

N/A

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team