Track concurrent keysigns as a metric

[CharlieMc0]

It would be helpful to track concurent keysigns via telemetry.

[kevinssgh]

@CharlieMc0 I've reviewed the code and I can provide a metric related to the number of active processors. What this means is an outbound transaction that is currently being processed. This will include the keysign and broadcast, Let me know if this is sufficient.

[kevinssgh]

Another solution would be to add a keysign manager to the TSS signer that keeps track of the number of concurrent keysigns. This will require a bit more work but will be more accurate.