Refactor Snippet Edit File field to Vue

What does this MR do?

The MR refactors the second bit of Edit File field, namely, the blob editor itself to Vue.

NOTE: this is a part of a larger effort of refactoring Snippet edit form to Vue, hence no CHANGELOG entry has been provided just yet

Important notes:

• The work in this MR is done behind the :snippets_edit_vue feature flag.
• For this particular MR, another feature flag might get into play (:monaco_snippets) that replaces ACE editor with Monaco's Editor Lite. This replacement is already in master and is not in the scope of this MR. However, this combination of two feature flags on the same field gives four scenarios for testing (see screenshots below) to make sure things do not get broken.
• Since this is a WIP to some extent (in the context of the larger effort, as mentioned above), this component is not rendered in the form just yet and will be enabled in one of the later MRs. To click test the functionality now, you can download the patch to apply additional changes locally.

Screenshots

	Before	After
🛑 :monaco_snippets 🛑 :snippets_edit_vue
✅ :monaco_snippets 🛑 :snippets_edit_vue
🛑 :monaco_snippets ✅ :snippets_edit_vue	Note: :snippets_edit_vue didn't exist, hence the rendering is driven only by the state of :monaco_snippets
✅ :monaco_snippets ✅ :snippets_edit_vue	Note: :snippets_edit_vue didn't exist, hence the rendering is driven only by the state of :monaco_snippets

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

References #207240 (closed)