refactor: Use a common build_recurrent_state method that is cache-agnostic
This reduces the code duplication between the different build_rs impls and
also retains a similar signature to the previous build_recurrent_state
method while standardizing on the input-dispatched build_rs implementation.
Branch: HybridRecurrentCache
Signed-off-by: Gabe Goodhart <ghart@us.ibm.com>