Align definitions of acuity in classification register with nhp_data

[yiwen-h]

Definitions here https://github.com/The-Strategy-Unit/nhp_data/blob/38c68b59715daea218f4eea1e00cd381bbd41cb8/src/nhp/data/raw_data/ecds.py#L58-L64

What's the best way to do this - just link to nhp_data? otherwise we risk having it defined in two places - need to remember to update both if anything changes

this is used in CLASS_AE_MINOR, CLASS_AE_MAJOR and CLASS_AE_RESUS

[paulseamer]

@yiwen-h The difference is that this framework references the ECDS_Description field whereas the NHP data pipeline references SNOMED_UK_Preferred_Term . Same thing just a different descriptor. For consistency, I'm happy to update this framework. I think it's only the 2 A&E fun area pages that reference the descriptors.

From ECDES ETOS v4.0.8 https://digital.nhs.uk/data-and-information/data-collections-and-data-sets/data-sets/emergency-care-data-set-ecds/ecds-guidance

| ECDS_Description | SNOMED_Code | SNOMED_UK_Preferred_Term |
| 1 - Immediate care level emergency care | 1064891000000107 | Immediate resuscitation level emergency care | 
| 2 - Very urgent level emergency care | 1064911000000105 | Very urgent level emergency care |
| 3 - Urgent level emergency care |1064901000000108 | Urgent level emergency care |
| 4 - Standard level emergency care | 1077241000000103 | Standard level emergency care |
| 5 - Low acuity level emergency care |1077251000000100 | Non-urgent level emergency care |