Consider including textual/file position for CIF common checks violations

From !399 (comment 1033269):

I must say however that while indicating a position by a name is nice, a line number would be a useful indication where to look for the name. Can that be added if it exists?

We could consider this, taking into account that:

• We may not always have position information (for instance due to preprocessing before doing an unsupported check), so this should be optional extra information.
• We may have imports, so this would need file/line/column information, similar to how the type checker for instance reports it.
• This may require an absolute path to resolve against, to get proper relative paths for the context where the violations are reported.