Change default_enabled value of FF in usage data

What does this MR do?

While working on an issue, I realized that we don't consider the default_enabled value of each individual usage_data_xxx feature flags. We assume they are enabled by default.

It is recently introduced that we can use default_enabled: :yaml for feature flag checks.

In this MR, I changed the usage of Feature.enabled?(:"usage_data_#{event_name}", default_enabled: true) to Feature.enabled?(:"usage_data_#{event_name}", default_enabled: :yaml) in Gitlab::Utils::UsageData.

Usage data feature flags that have default_enabled: false in their YAML definitions:

• usage_data_track_ecosystem_jira_service
• usage_data_static_site_editor_merge_requests
• usage_data_static_site_editor_commits
• usage_data_code_review_aggregation

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