Initial KeysInUse integration

[mamckee]

This PR adds optional KeysInUse logging following the original formatting defined for https://github.com/microsoft/KeysInUse-OpenSSL

• The KeysInUse feature is hidden behind a compile time flag and must be enabled at runtime either by config or environment
• Logging is handled by a dedicated logging thread to minimize overhead on crypto
• All KeysInUse errors are logged to a separate file to avoid polluting the error stack
• Supported private key operations for logging:
  • RSA sign
  • RSA decrypt
  • ECDSA sign