Support for simultaneous delta and cumulative temporality

[srikanthccv]

The current implementation only supports one temporality at a time. A metric has to be either delta or cumulative. This makes it hard to switch from one to another. For instance, I want to recommend adding a cumulative delta pipeline for metrics for end users. This would be fine for new users, but existing users can't transition without breaking things. Make query-service support both in any combination, i.e. both temporalities are sent, cumulative in the past but delta now, the delta in the past but cumulative now.