Tell robot when to dry/soak

[DominicOram]

The robot needs to occasionally dry/soak so that it cleans off any ice that has built up on the gripper. This operation takes ~95s and the robot can't be used in that time. The current logic for this is that every 90 minutes the robot will internally set a flag to say "after the next load dry" and will then dry on the next load. This was good behaviour when we knew a collection would take >90s. However, when we start skipping bad samples this assumption will not be true any more. e.g. the worst case is:

1. Robot sets internal flag to say it's time for a dry
2. We load
3. Robot starts drying
4. We find the pin is too short/long (this takes ~5s)
5. We now have to wait ~90s for the robot

To improve this we should instead trigger the dry/load on the robot once we know we're going to perform a long operation e.g. after we have done an XRC for a native collection and know that we will have diffraction. However, we will also want to make sure the robot does still do a dry/soak at some point even if we are not doing any native collections. Therefore the logic will look something like:

1. Hyperion sets a "good opportunity for dry" PV on the robot after the first successful XRC of a native collection
2. The robot checks if it's been 90 minutes since the last dry, if so it will do a dry
3. If the robot doesn't see this PV being set after 120 minutes of still not drying it will just dry on the next load

Acceptance Criteria

• The above logic is implemented

[graeme-winter]

I'll note for the record that this is a very nice problem to have

[DominicOram]

I'll note for the record that this is a very nice problem to have

Yh, it's potentially a case of me getting to deep into trying to optimise but worth noting down as it shouldn't be that hard