[FIX] l10n_ch: fix QR-bill pdf report so that it matches the spec

Using it as a parf of the regular invoice pdf report was wrong, as this report is subject to the margins defined in its paper format; causing issues as for the rendering of the QR report, which must be displayed at a precise location (just like ISR). wkhtmltopdf doesn't allow having different margin values in the same file, so we did just as for ISR, and now generate QR-bill in a distinct pdf.

[IMP] l10n_ch: add receipt part to QR-bill pdf report

closes odoo/odoo#50338

Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>