Blob refactor: Expose initAuxiliaryViewer method

What does this MR do?

This MR is part of a bigger effort to Refactor Repository Browser to 1 Vue Application.

In this iteration to Ensure Auxilary viewers work as expected we move the initAuxiliaryViewer method outside of the BlobViewer class and export it. This enables us to call the initAuxiliaryViewer method in the refactored blob viewer as well (follow-up MR).

Description	MR
Expose initAuxiliaryViewer method	This MR 👈
Fix the Auxiliary viewers	follow-up MR

Screenshots or Screencasts (strongly suggested)

No visual changes are expected, Auxiliary viewers still works as expected when the refactor_blob_viewer FF is off.

Does this MR meet the acceptance criteria?

Conformity

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• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
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• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #334789 (closed)