Provide metrics around HSM operations.

We are doing HSM performance testing and decided it would be valuable to add metrics around PKCS11 calls so we can easily see how many calls are being made and, more importantly, how long the calls are taking.

This would help users be able to quickly spot HSM related issues vs issues in fabric itself.

Some possible metrics, although this is off the top of my head, so please provide what you think makes sense:

• Time each call takes
• Number of calls
• Session Pool size?
• Metrics on sessions that are removed from the pool because they are invalid?