Add sequence numbers to alloc FE progress update messages to not require current/total change for update to extend timeout

[eabatalov]

Add sequence numbers to alloc FE progress update messages to not require current/total change for update to extend timeout.
Reconcile on Executor side using the sequence numbers instead of the current, total values.

Also change current and total parameters to optional. Users don't always know what's their current step or total number of steps. This sequence number change allows us to do this.