Range requests from existing downloaded files

The Issue

Currently, we allow range requests to happen from the blob files themselves. In the case where I downloaded a file locally but didn't save blobs (or lost them), I should be able to perform range requests on the file itself without having to redownload the blobs.

System Configuration

• LBRY Daemon version:
• LBRY App version:
• LBRY Installation ID:
• Operating system:

Anything Else

Screenshots

Internal Use

Acceptance Criteria

Definition of Done

• Tested against acceptance criteria
• Tested against the assumptions of user story
• The project builds without errors
• Unit tests are written and passing
• Tests on devices/browsers listed in the issue have passed
• QA performed & issues resolved
• Refactoring completed
• Any configuration or build changes documented
• Documentation updated
• Peer Code Review performed

No file, test, or entry point is identified in the issue. Start by tracing how range requests are served from blob files and how downloaded files are tracked, then define tests for serving ranges from an existing local file without redownloading blobs.