minor naga span updates

[brody4hire]

Connections

trigger is reducing dependency on std::error::Error for other PR: #6938

(help with no-std support as requested in issue: #6826)

Description

• move internal naga span::AddSpan code to keep internal AddSpan trait & impl together
• remove where dependency on std::error::Error from AddSpan impl
• add blank lines & returned output type comments to AddSpan & MapErrWithSpan traits
• update MapErrWithSpan to be pub(crate) trait

NOTE: I am submitting this with multiple commits to hopefully keep these proposed updates as clear as possible. I would be happy to squash if needed. I would also be happy to revert the MapErrWithSpan trait visibility update if needed.

Testing

see checklist below

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[cwfitzgerald]

Wow this was just flat out not needed?

[cwfitzgerald]

NOTE: I am submitting this with multiple commits to hopefully keep these proposed updates as clear as possible.

Sounds good, will rebase-and-merge these.

I would be happy to squash if needed.

We always have the squash-and-merge button, so feel free to be as messy with commits as you want, as long as you want us to review as a whole as opposed to commit-by-commit.

[brody4hire]

@cwfitzgerald it looks to me like you did some kind of rebase merge, with 4 commits added to trunk now. Not a big deal but not as I had expected