Migrate from Prettier to oxfmt #19223

Replace Prettier with oxfmt for code formatting. Oxfmt is a Rust-based, Prettier-compatible formatter that's ~30x faster. Config migration is minimal as Prettier JSON configs carry over with a rename.

Known issues

• Problems formatting HTML and Ember template files in the repo
• Alpha-stage bugs may cause formatting inconsistencies in edge cases

Scope

• Replace .prettierrc with .oxfmtrc.json configs
• Update format scripts and VS Code settings to use oxfmt
• Add fix and check formatting scripts
• Validate output parity with Prettier across the monorepo

Depends on

• Oxfmt reaching beta stability
• Verifying HTML output.

Tracking PR: #19200