Update UI for ICD-10 codes with different descriptions in 2016 vs 2019

[rw251]

The combined 2016/2019 ICD-10 release contains some codes whose descriptions have changed. If this change is significant then we will display a warning banner (#3123). But even if not a significant change, we may want to show the user the different descriptions. This ticket covers:

• Deciding what to display in the main tree view (i.e. just 2019 or just 2016 definition)
• Deciding what to display in the "more info" modal pop up
• Implementing the changes

[rw251]

I think we should display the 2019 description, falling back to the 2016 description for codes that only appear in 2016. This is because:

• the majority of codes (~16,000) have identical descriptions so it doesn't matter for them
• most of the remaining codes (~100) have near identical descriptions where the clinical meaning is identical e.g. minor things like objects becomes object(s), or synonyms like Norwalk agent and Norovirus. As the meaning is identical, there is no reason to display both, and the 2019 one would be fine
• the remaining codes (~50) have descriptions that could be clinically different (depending on the exact codelist). For these we display a big warning banner, along with both definitions - so there is no extra reason to display both descriptions in the tree view.

The "more info" modal should display both (when they differ), but no need in the main builder tree view - or when viewing a codelist.

Update The above argument shows it doesn't matter which definition we show, rather than we should show 2019. There is in fact maybe a stronger case for displaying the 2016 descriptions (falling back to 2019 for codes that only appear in 2019):

• The NHS 2016 definitions fix some typos that persist into the 2019 edition
• The APCS table is accessed more often than ONS deaths (TODO - check this)

[rw251]

1. Code with multiple descriptions that we think are clinically different

2. Code with multiple descriptions that we think are the same