Diagnostic cache viewer

[smashwilson]

Track the usage of cache data. Add a pane item that displays the current cache contents, live, and allows selective or bulk cache flushing. Totally low-priority tinkering from me.

Here's what I've got so far, pardon the Developer Art 🎨:

• Give the Cache an event emitter and an onDidUpdate event.
• Store extra cache entry metadata: age and hit count.
• Display the cache data in a PaneItem triggered with github:show-cache-diagnostics.
• Sort cache entries within the table: alphabetic by name, oldest first, newest first, most hits, fewest hits.
• Convert the cache key column to buttons that evict that cache entry on click.
• Add a button to flush the entire cache at once.
• Truncate cache entry values at some reasonable maximum size.

[smashwilson]

Eh this might be handy.