SANS: ZOOM standard instrument configuration and polarised beam modes

The instrument should have defined default measurement modes and helper files to reset motors to default values. This becomes in particular helpful for polarised to simplify flicking between different spin state modes in a bespoke measurement mode.

Start by locating the existing SANS/ZOOM instrument configuration and motor-control entry points, then inspect how measurement modes and spin states are currently represented. Define the default measurement modes and helper files for resetting motors, including the polarised beam modes, and verify that switching modes restores the intended defaults.

Written by the indexing model from the issue text.