Simply move the code into a function.

This function is responsible for storing the verified state response in
the memory.

Same as the last commit, just move the code into a new function.

This will be reused in the subsequent commit.

…ed()`

Make it clearer about what data are written.

…e as `process_state_verified()`

We can see clearly the common logic between `process_state_verified()`
and `process_state_unverified()`, which will be extracted further in the
next commit.

Before this commit, every commit is an equalvalent rewrite.

This commit modifies the origin logic by moving the child_key_value
in `process_state_verified()` to the same place in `process_state_unverified()`.

Please review this very carefully.