[jb] performance and health dashboard

[akosyakov]

After #9515 we can collect metrics on individual workspace pods.
As performance testing [1] showed important metrics in context of JB are:

• allocated and used heap memory
• completions and typings latencies in both editor and terminal
• frequency and duration of background tasks, like indexing, dependency resolution

[akosyakov]

• Heap utilisation is covered by [jb]: monitor low memory notifications #10558
• For latencies we need APIs in GW: https://youtrack.jetbrains.com/issue/CWM-6417/Expose-performance-and-health-stats-of-JB-Client-to-GW-plugin