Use annotate-snippets for rustc diagnostic output

[nikomatsakis]

Metadata
Owner(s)	@estebank, @Muscraft
Team(s)	compiler
Goal document	2024h2/annotate-snippets

Summary

Switch to annotate-snippets for rendering rustc's output, with no loss of functionality or visual regressions.

Tasks and status

• Reach output parity of rustc/annotate-snippets
  • Port a subset of rustc's UI tests (@Muscraft)
  • Make list of current unnaddressed divergences (@Muscraft)
  • address divergences (@Muscraft)
• Initial use of annotate-snippets
  • update annotate-snippets to latest version
  • teach cargo to pass annotate-snippets flag (@estebank)
  • add ui test mode comparing new output
  • switch default nightly rustc output
• Production use of annotate-snippets
  • switch default rustc output
  • release notes
  • switch ui tests to only check new output
  • dedicated reviewer (compiler )
• Standard reviews (compiler )

[nikomatsakis]

This issue is intended for status updates only.

For general questions or comments, please contact the owner(s) directly.