Fix indentation lines (#6134)

[NomisIV]

Closes #6134.

This is my first contribution and I'm honestly surprised at how quick I was able to implement the fix.
Criticism is welcome - I don't know what I'm doing xD

[pascalkuthe]

Good catch, this particular mixup of tab width and indent width was missed in #5918.

[NomisIV]

Btw, there's something fishy with where the start of the indentation lines is calculated:

As you can see, they are drawn over the line numbers and the line gutter...

I can try to fix this in another PR, when I understand how starting_indent works

EDIT:
It seems that the issue is the implicit flooring of the number with the integer division in starting_indent. I tried casting the division to a float and ceiling it instead and then casting it back to usize, and now it works, but it looks kind of ugly though...

EDIT2:
This looks better

            starting_indent: (col_offset + indent_width - 1) / indent_width
                + editor_config.indent_guides.skip_levels as usize,

I could just push this change in this PR too to reduce the overhead of another PR

[pascalkuthe]

Ah yeah the upwards rounding is the correct fix. This bug seems to exist eversibce indent guides were added but the reason it wasnt visible.before is that gutters were drawn after the text in the past so the additional indent guides were overwritten but since #5420 gutters are drawn as a gemric decrostions which get rendered on the fly just before the text on the same line is drawn SL.the existing bug is moticable now.

It would be great if you fixed the rounding inside this commit. However a small.nit: foe upwards rounding integer division col_offset / indent_width + (col_offset % indent_width != 0) as u16 prevents overflows and is faster as module and div are usually computed by the same instruction

[pascalkuthe]

LGTM, this cleans up some loose ends from #5420 and #5918