Fix fmt panic for const inside trait and abi

[sdankel]

Description

Closes #5008

The panic happened because the formatter was adding two ;s after a constant declaration inside of a trait. It happened for ABI too, so it's fixed for both with tests.

I'm working toward the goal of making it so the formatter never panics, even for sway files that do not compile.

I made it so, when a sway file does not compile, it does not cause the formatter to panic. Now it prints an error message.

I'm checking in this simple bash script that runs the formatter against every sway project in the repo. Fixing these bugs brought the # of panics from ~35 down to 15.

I verified that the CI step that checks the formatting of sway docs is still working.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[eureka-cpu]

Happy to approve once CI checks pass, nice one @sdankel !

[JoshuaBatty]

LGTM