[SPARK-22103] Move HashAggregateExec parent consume to a separate function in codegen

## What changes were proposed in this pull request?

HashAggregateExec codegen uses two paths for fast hash table and a generic one.
It generates code paths for iterating over both, and both code paths generate the consume code of the parent operator, resulting in that code being expanded twice.
This leads to a long generated function that might be an issue for the compiler (see e.g. SPARK-21603).
I propose to remove the double expansion by generating the consume code in a helper function that can just be called from both iterating loops.

An issue with separating the `consume` code to a helper function was that a number of places relied and assumed on being in the scope of an outside `produce` loop and e.g. use `continue` to jump out.
I replaced such code flows with nested scopes. It is code that should be handled the same by compiler, while getting rid of depending on assumptions that are outside of the `consume`'s own scope.

## How was this patch tested?

Existing test coverage.

Author: Juliusz Sompolski <julek@databricks.com>

Closes #19324 from juliuszsompolski/aggrconsumecodegen.