Auto merge of #114962 - darklyspaced:debug, r=est31

adds a column number to `dbg!()`

this would be very nice to have for a few reasons:
1. the rfc, when deciding not to add column numbers to macro, failed to acknowledge any potential ambiguous cases -- such as the one provided in #114910 -- which do exist
2. would be able to consistently and easily jump directly to the `dbg!()` regardless of the sutation
3. takes up, at a maximum, 3 characters of _horizontal_ screen space

fixes #114910

Author: bors