Bump dependency on cbf-emulator to ^7.0.0

On the one hand this brings in breaking changes, but on the other it keeps this repository aligned with the latest developments in the cbf-emulator package and requires little effort to update.

Note also that the previous version of cbf-emulator we depended on (3.2.0) had unbounded dependency constrains, and therefore it was pulling in versions of receive-core that were incompatible.

Signed-off-by: Rodrigo Tobar rtobar@icrar.org