[wip] Linearizable LeaseLeases

[endocrimes]

Rough look at what a Linearizable LeaseLeases would look like.

Opening before adding a ListLeases API to get feedback on using linearizableReadNotify which based on reading the impl seems like it should be safe without needing to forward to the leader.

[serathius]

Not sure if we should introduce this field when we are planning to introduce ListLease. cc @ptabor

[ahrtr]

Not sure if we should introduce this field when we are planning to introduce ListLease. cc @ptabor

I think It should be a three steps plan:

1. Step 1 is to introduce a linearizable field;
2. Step 2 is to deprecate the LeaseLeases;
3. Step 3 is to add ListLeases.

[serathius]

PTAL #13690
I we will use different approach to fix leases.

[ptabor]

I think we still need linearizable leases: #13915

[ahrtr]

I think we still need linearizable leases: #13915

Yes, I agree. At least we need linearizable ListLeases at first.