Do not render Source Editor by default for the repository files

What does this MR do?

Introduces the conditional loading of the Source Editor component (formerly known as Editor Lite) in the repository browser. The editor is loaded o nthe view only in case:

1. rawContent is specified on the viewer, AND
2. the :refactor_blob_viewer feature flag is enabled

This is required to prevent monaco chunk to be loaded everywhere where the simple_viewer is used.

Screenshots (strongly suggested)

	Before	After
Snippet

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because the MR fixes a regression introduced in the same milestone.
• 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

Related to #327782 (closed)