make relative locatoin reliable and precise

[bobzhang]

@Guest0x0 As discussed offline, we need the relative location to project_root_path be reliable(regardless of whether using src field or not), since both moon and moonc konw such info, this is doable, having reliable error location is helpful for AI Agent to quick locate the failure place.

we are going to merge this, it does not do any harm, but we need follow up work to clean this up

Originally posted by @bobzhang in #3035 (comment)