fix(pds): handle `com.atproto.sync.subscribeRepos#handle` messages

[mileszim]

Summary

• PR updates PDS RepoSubscription to handle the #handle message
  • #handle message was getting dropped and throwing log warning
  • now it inserts did + handle into the did_handle table if it isn't already there
• Also refactors a couple of methods in the class/file to align more with bsky implementation

Packages Affected

• [x] bsky

How is this tested?

• Unsure how to add test case for this, but still looking