Multimedia: Add platform configs for additional media backends


This patch adds extra platform configs when running tests, that only
apply to Qt Multimedia. They allow qtmultimedia to run extra tests using
other runtime configurations, such as separate mediabackends.

Pick-to: 6.12
Change-Id: Ib14476f2f7d7e010717b6c8888d900155e10faa5
Reviewed-by: Tim Blechmann <tim.blechmann@qt.io>
commit1f4bb9e796177b2298602da1b4db6783e22c0d21
parent362d88772c7bc56aa26d113ce03fdaf79be188ac
authorNils Petter Skålerud <nils.petter.skalerud@qt.io>
committerNils Petter Skålerud <nils.petter.skalerud@qt.io>
commit timeWed, 14 Oct 2026 14:54:29 +0000