fix: generate valid toml when outputting nested structs

[TomAFrench]

Related issue(s)

Resolves #934

Description

Summary of changes

toml wasn't automatically ordering fields before tables in the toml it generated so we were manually partitioning the input map to ensure this happens. We however not we're enforcing this for nested tables which also include non-table fields.

toml has been since updated to handle this automatically so I've updated to the new version.

Dependency additions / changes

toml has been bumped to 0.7.2

Test additions / changes

Added a regression test for #934

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.
• This PR requires documentation updates when merged.

Additional context