Ensures the back link chevron-left icon is vertically aligned with the
text at all font sizes.

This ensures that the back breadcrumb chevron icon is
vertically aligned with the text, even at large font sizes.

Ensures that the action link icon is vertically aligned with the text,
even at large font sizes.

Vertically aligns the pagination icon with the pagination text, even
with large font sizes. This calculation was determined experimentally by
manually positioning the icons at a variety of font sizes, and succeeds
in appearing to vertically align the icon in the majority of cases, with
only very small font sizes looking slightly out of place. The removal of
`margin-top: 0` for `media-type: print` does not appear to affect the
output when printing.

Use `/ 10px` then `* 8px` rather than `* 0.8px` so that SASS doesn't
error. Still functionally equivalent.

Vertically aligns the chevron icon with th 'more' text in the header
navigation, when it is visible.

Ensures that radio buttons are vertically aligned with the label, even
with larger font sizes.

Ensurees that the chekboxes/ticks are vertically aligned with the label
text, even with large font sizes.

Esnures that tick/cross icon is vertically aligned with text, even at
large font sizes.

Updates the regression equation for the do/don't tick cross, so that the
backstop tests pass.

Uses a regression function to position the checkbox & tick, rather than
always centering it in the middle of the paragraph, so as to pass the
backstop tests.

Adjusts the pagination icon alignment regression calculation so that the
backstop tests pass.

Uses a regression based on rem, so as to pass the backstop tests and retain
some consistency with previous behaviour. This is the saame regression as
for checkboxes.