rspirv2 disassembly

[Firestar99]

We released rspirv2 🎉

• best reviewed commit by commit
• last commit "switch dis preset to default" has a ton of bless changes that don't need to be reviewed, since I'm only changing the disassembly settings for prettier disassembly
• rather, review the blesses in "replace disassembler*" where actual differences between rspirv and rspirv2 are visible
• while you're reviewing this, please also approve ci: split compiletest target-envs into steps #533