Rename the newly added snippet blob raw route

Summary

We recently added two new routes for handling raw snippet blobs - however the naming convention used was slightly different between the project and personal snippet variations.

We should align so rather than having:

Project Snippets: namespace_project_snippet_blob_raw_*

Personal Snippets: snippet_raw_*

We should change personal snippets to be snippet_blob_raw_*

Improvements

This should make the two routes more consistent and so easier to use, as well as associating the personal snippets variation to the controller (Snippets::BlobsController).

This will also help to differentiate between the existing/old raw snippet route raw_snippet_*

Risks

None, neither of these named routes are currently used.

Involved components

config/routes/snippets.rb