Expose blob_path for vulnerability occurrences

What does this MR do?

This provides the path to the file that caused a particular vulnerability occurrence. It is added to the location hash of the vulnerability occurrence. This will be utilized in a separate frontend change to provide a clickable link to the offending file, with highlighted lines where appropriate.

What are the relevant issue numbers? #9283 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• 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