feature: add support for disabling the primary label line/col information

[Zij-IT]

This is an attempt to tackle #91 by using the with_primary_span_start (default) and without_primary_span_start options.

This keeps the current behavior unchanged, but allows the user to turn off the line:col information displayed for a report whose primary span extends across multiple lines. A short example:

// This
  × decoding error
   ╭─[2:5]
 1 │ malformed
 2 │ h�XYZ
   ·   ┬
   ·   ╰── valid data here
   ╰────

// Becomes
  × decoding error
   ╭────
 1 │ malformed
 2 │ h�XYZ
   ·   ┬
   ·   ╰── valid data here
   ╰────