Update blob header to support delete button group

What does this MR do?

MR	Changes
this MR	Convert to button group and add delete button
TBD	Add blob delete modal
TBD	Add validation directive to delete form

In this MR, we are updating the blob header to support the button group, where we will include the existing "replace" button and the new "delete" button.

Before	This MR

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 to get to the Blob page
3. You will see a button group with the "Delete" button

Note: the "delete" button when clicked won't trigger anything. We will add the delete blob modal in a separate MR in favor of smaller MR and working 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)