add read/write multi calls
A BAKE client may want to do iovec-style reads/writes to a given BAKE region to avoid having to do data sieving on an entire region or issue multiple RPCs to access the data of interest.
A BAKE client may want to do iovec-style reads/writes to a given BAKE region to avoid having to do data sieving on an entire region or issue multiple RPCs to access the data of interest.