MARI: Set up sample changer with new homing mode

As of https://github.com/ISISComputingGroup/IBEX/issues/5729 the mclennan has the homing mode required for the MARI rotating sample changer. We should do the following to set MARI up to use this.

## Acceptance Criteria
* There are two configs for the different sample changer types
* The direction is set into the config such that positive moves in both turn the device in the correct direction
* The homing routine is set so that both move in the correct direction when homed
* The offset is set in the configuration rather than the script
* Test this on the hardware with Duc's script
* Duc's script moves 89.4 degrees for each sample rather than 90 to correct for an inaccurate motor resolution. Correct this and confirm that after a large number of moves the sample changer is still moving accurately (see `NDXMARI/c$/scripts/test_sample_changer.py` to help with this