Blob refactor: add blob delete modal

What does this MR do?

MR	Changes
!64666 (merged)	Convert to button group and add delete button
this MR	Add blob delete modal
TBD (Issue #335743 (closed))	Add validation directive to delete form

This MR adds a delete blob modal. It's part of the refactoring from HAML to Vue for the entire blob content > &5531 (closed).

Button	Modal

Here's the HAML file for reference:

• app/views/projects/blob/_remove.html.haml
  • app/views/shared/_new_commit_form.html.haml

Testing Case

This feature is behind a feature flag, to turn on:

rails c

Feature.enable(: refactor_blob_viewer)

1. Navigate to Repository > Files.
2. Click on a file.

Deleting a file

After deleting a file in the same branch, you will get redirected back to the files page.

Modal	Redirect to Files Page

Deleting a file in a new merge request

When deleting a file in a new merge request. The deleted file will appear in the newly created branch and you will get redirected to the "Create MR" page.

Modal	Redirect New MR Page

Note

There is no new behavior that is introduced with this MR. We are simply moving the delete blob modal into Vue. Note, because we're still in the early stages of the refactoring, there are still missing components that have not migrated to Vue; hence, we're leaving the feature specs updates until the migration is at a more complete stage. This feature is behind a FF, so we have some safety net to work on this iteratively 💪

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• 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.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• 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 #333773 (closed)