Split safety impact into supplier / deployer safety impacts

[ahouseholder]

(This was actually from @j--- I think, I just copied & pasted the text into the issue, so be careful when dereferencing the pronoun "I" in the below)
"Safety Impact" probably needs to be split up into one for the vendor and one for the applier. I think the vendor one could be re-used by a coordinator. I'd call it "public safety impact" or some such. The Applier one would be "situated safety impact" or some such.

[j---]

This is also related to feedback from https://blog.secursive.com/posts/critical-look-stakeholder-specific-vulnerability-categorization-ssvc/
Basically that "safety impact" as written in v1 is too complicated / fine grained for the supplier to provide accurately.

[ahouseholder]

Updated plan based on recent discussions:

• Combine none/minor categories into one, leaving 4 levels
• Split safety into separate decisions for supplier / deployer
• Supplier is focused on public_safety
• Supplier maps those 4 levels to 2 (maybe 3) public_safety_impact categories (L/H or L/M/H)
• Deployer is focused on situated_safety
• Deployer version integrated with Mission Impact Merge situated safety impact and mission impact into a unified factor #7 in a ~4x4 table that maps both dimensions impact into a combined 3 safety&mission_impact categories (L/M/H)

End result for Deployers will be that safety & mission will go from 5x5=25 possibilities to 4x4 -> 3 categories which should reduce the complexity of the deployer tree considerably.