Store and log timing/IO traces

[PerilousApricot]

• Add (optional) per-file tracing for all the I/O requests against the file backing store. Allow this to be later extended to trace the I/O against the higher-level caching layer.
• Add (optional) timing tracing of
  • Metadata deserialization
  • Basket I/O
  • Basket decompression
• Add config option to dump these info to the console

[PerilousApricot]

Hmm, need to somehow transmit these data from the executors back to the driver

[PerilousApricot]

The logging is done and implemented for both the single-process and distributed cases, and is used for unit testing. Exposing the data in production can be explored later