Per-key locking, avoid lock for GetEntriesAsync#790

Kaliumhexacyanoferrat merged 4 commits intoKaliumhexacyanoferrat:mainKaliumhexacyanoferrat/GenHTTP:mainfrom

MarkCiliaVincenti:AsyncKeyedLockMarkCiliaVincenti/GenHTTP:AsyncKeyedLockCopy head branch name to clipboard