Beam control linkages (allocate/release, configure, scan, etc)

Whilst SP-1718 extended TPM configuration capabilities, further to form and control beams on AAVS (and beyond) we need to finish implementing the linkages between the beam devices and the tiles. We must fill any remaining gaps in resource management (de-allocation?). To implement the Scan command we need to start a PointingJob and connect this to the TPM delay control.

To facilitate AAVS operation (i.e. in the absence of a TM system) we might consider implementing appropriate 'back-door' functionality. For instance, a driving notebook could set beam pointing for a strong source such as the Sun or galactic centre and demo a real observation. This would use the methods in station/point_station.py. In the simplest case this would set the beam for a drift scan. The more advanced case would run regular updates to achieve scanning / tracking.

In PI18 it was expedient to sidestep some of the SubarrayBeam allocation/configuration work, leaving some of this functionality in Subarray rather than fulfilling the planned architecture. We will implement SubarrayBeam as intended, so as to abstract beam functionality, removing station-level beam responsibilities from the Subarray device.