fdo#79078 restore transparency in SVG export

Change-Id: I5bdf6c3b313a73126cb692e5101836f424a2fc08
Reviewed-on: https://gerrit.libreoffice.org/9442
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>
Resolves: fdo#79181 drop hidden shape and drop negative clip rect

and just resize bg to the desired size. The negative clip is getting
applied against an assumed 0,0 origin and so we're missing the bottom
of the unclipped image.

Change-Id: I9d7c5d17de15176d103690898281c6b875b560ca
(cherry picked from commit f5251d35043cab1117e12677f0c40f3e849f3e1c)
(cherry picked from commit e71fccd0729340c666e2b32dc09cdc9eff246568)
Reviewed-on: https://gerrit.libreoffice.org/9486
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>