fix: Keep comments and attrs when extracting struct from enum variant

[DropDemBits]

Fixes #6730

Still unsure if existing visibilities of fields should be forced to pub (which is what was previously done), or if it's okay to keep it in the extracted struct.

[Veykril]

I imagine pub was always unconditionally inserted as you wouldn't usually have vis mods on variants/variant fields since they are only allowed for parsing but rejected later one. In the end this shouldn't make a difference therefore since we don't generate incorrect code in the end. So this change seems fine to me.

bors r+

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)

[lnicola]

changelog fix (first contribution) keep comments and attributes when extracting struct from enum variant.