internal/core/adt: record more error positions
Method: replace `ctx.Str(x)` arguments to formatting
with `x` and let the error methods do the conversion.
This gives access to position information as well, which
can then be added to the errors.
This has the additional benefit that this will allow lazy
expansion of error printing down the road.
Note that in some cases we now drop the "main"
position as it would result in too much redundancy.
In tests this manifests itself as a slight change of
the column position.
Fixes #905
Closes #129
Issue #52
Change-Id: I044cf34b9718f05553139974c6c166d2630568e6
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9446
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Paul Jolly <paul@myitcv.org.uk>