os: add package_size to TransferRequest (#90)

* add os package to compile_protos.sh

* os: add package_size to TransferRequest

This will allow the target to know whether an OS package is
 going to exceed the maximum possible size before the
 client starts streaming any bytes to the target.
Currently, if the client was to transfer a larger-than-allowed
 OS package, the target would not be able to detect this until
 midway through the transfer_content stream.

* os: increment version to 0.1.2

Version incremented following the addition of the
 package_size field to the TransferRequest type

* os: update package_size description

* empty commit to rerun broken github actions job