Resolve "New re-usable component for Blob File Header"

What does this MR do?

Provides the last bit for the "New re-usable component for Blob File Header": namely, the header component itself that lays out and orchestrates all the relevant components (already merged).

This is supposed to be a stateless component for the purpose of it being used in both: Vuex- and Appollo-driven applications. Hence all the data management should happen in the parent component that contains the header (and sets the original state with props), while header components communicate back through eventHub.

NOTE: Since this MR is the part of a larger feature of refactoring Snippets view to Vue, this MR doesn't have own CHANGELOG entry.

Screenshots

⚠ Note, the visual difference in the icons has been handled in the respective components and should not be evaluated as part of this MR

	Before	After
Simple viewer
Rich viewer

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

Closes #196794 (closed)