Avoids 'system' imports

Reworks revision uris to use a packed authority for better stability

Need to defer this more, but this should help some

Since microsoft/vscode#3025 is now fixed, file watching works outside the workspace

Ensures known SCM repos are known to GitLens

Should hopefully no longer be required

Adds new visited paths trie for fast lookup of seen paths (to avoid git calls)
Replaces the tracked cache with a paths trie
All tries are case aware based on os and scheme (if uri based)

Adds new detectNestedRepositories setting to improve performance
Automatically handles nested repos for open document and remaps paths
Reworks isTracked for perf & nested repo detection

Changes excludes to a Set for faster matching
Splits getRepository into get & create (also removes async for get)
Replaces repo path methods with repo versions (part of moving away from string paths)
Renames getRemotes to getRemotesWithProviders & getRemotesCore to getRemotes

As `.git` is a file, not a directory

Adds unit testing (just for the trie for now)

Cleans up overloads

Avoids debouncing repo change events
Allows for immediate resetting up data, but still debounces updates
Also avoids a repo change event clearing valuable data after the fact

Remembers & attempts restore of last known git path (per workspace)
Races a git path search while getting the path from SCM

Renames content method for clarity

Should help with eventual testing

Consolidates to node-fetch 2.6.7 as Octokit requires v2

- Adds proper error handling & messaging
  - Handles uncommitted lines
Adds open prior blame to hover on uncommitted lines