Further fixes for #3120, Adds DOMPDF specific adjustments to prevent
full width linked images being cut-off as per last tweak.
This does not fix usage in smaller cases (tables) but tested on
master DOMPDF branch shows that will likely be fixed in next DOMPDF
upstream release.
DOMPDF fixes would break WKHTMLTOPDF presentation so system updated
to conditionally apply styles.
- Replaced iframe elements with anchor elements wrapped in a paragraph.
- Extracted PDF generation action to seperate class for easier mocking
within testing.
- Added test to cover.
For #3077