Multi-rotation scans part 2: nexus callbacks

[dperl-dls]

Towards #960

• Builds on https://github.com/DiamondLightSource/hyperion/pull/1461
• Extends the rotation nexus callback a tiny bit to handle multi scans
• Adds a sim callback to test documents and a system tests to check files are linked correctly
• Discussion of how to record rotation directions spun out to here: https://github.com/DiamondLightSource/nexgen/issues/261

To test:

1. Run tests