Add Support for Aggregates and GroupBy in Branches

[eneshoxha]

Adding support for Aggregate and GroupBy inside Branches. Also, implementation of Background and non-background Aggeregations and GroupBy states

[eneshoxha]

In this feature, we are going to implement the Background and non-background Aggeregations and GroupBy states.

[eneshoxha]

We are adding GroupBySilently and AggregateSilently functions in the stream.