Description of the change

This allows the compiler to be more honest about the source annotation for value declarations. During desugaring, theSourceAnn for a value declaration is replaced with a corresponding type declaration'sSourceAnn if it exists.

I noticed this while working on#4247 and it messes up the order for constructing the interval tree
which I intend to serialize into a file/use inpsc-ide as part of the type-on-hover stuff.

Another solution for this is to expand the annotation during desugaring such that both the annotation and value declaration is covered, but this changes behaviour in error messages.

Checklist:

• Added a file to CHANGELOG.d for this PR (see CHANGELOG.d/README.md)
• Added myself to CONTRIBUTORS.md (if this is my first contribution)
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)