Port new formatter

[doriable]

This PR replaces the legacy formatter with the new formatter,
based on the new compiler's AST printer.

All of the goldens that have changed have been tested for how
they would affect users/if they would create churn

• the new formatter adds a space for contiguous in-line block comments (should be a very rare case)
• the newline between declarations being source-aware will not produce any churn for any files that users have already formatted with the legacy formatter
• and the behaviour for detached comments is actually fixed between declarations

This also uses mutations to the new AST to implement the deprecation feature
in the formatter.

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	May 22, 2026, 10:34 PM