Implement connection manager

Nobody has claimed this yet.

## The Issue
Per a discussion on call this week, we don't have anything currently handling/optimizing for multiple downloads at the same time. The connection manager would support concurrency and efficiency when finding peers.

Handle scenario where a poor connection has to download the same blob from multiple peers, effectively reducing their bandwidth at a single peer which means a successful download is less likely.

## System Configuration

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

## Anything Else

## Screenshots

## Internal Use

### Acceptance Criteria
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### 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

The issue names no files, tests, or concrete acceptance criteria. Start by locating the existing peer-finding and blob-download paths, then clarify how concurrent downloads and peer selection should work. Done should include avoiding duplicate downloads from multiple peers, passing unit tests, and documenting the resulting behavior.

Written by the indexing model from the issue text.