Currently, to replace a component in an RMA shim, we need to build a new shim from all components. It's better if we can in-place replace components in an existing RMA shim. A common use case is updating HWID database. 

Implement a `image_tool` subcommand `rma-replace` to replace the components.
e.g. image_tool rma-replace rma.bin --hwid new_hwid_bundle.sh