VueTransformer uses nonsensical values for codeFrames.codeHighlights line numbers

[lol768]

I mentioned in my PR (#8499) that the code previews don't work and hypothesised I was doing something wrong.

Looking at the line numbers it was generating, they're all nonsensical:

line: err.loc.start.line + err.loc.start.offset,

I don't get what this is supposed to do, but it generates line numbers like 1483 in a 155 line file!

Looking at the Vue SFC compiler's code

https://github.com/vuejs/core/blob/fbd697a4b6c238147d661026836314862fd09221/packages/compiler-sfc/src/compileTemplate.ts#L307-L312

It's already adjusting the line numbers by an offset, and indeed if I change the code to not add this offset, the code previews start to work fine:

if (err.loc) {
  diagnostic.codeFrames = [{
    filePath,
    codeHighlights: [{
      start: {
        line: err.loc.start.line,
        column: err.loc.start.column
      },
      end: {
        line: err.loc.end.line,
        column: err.loc.end.column
      }
    }]
  }];
}