tests: add testMappedFrameSurvivesCameraStop


Validate mapped frames survives stopping cameras, possible regression
tests when borrowing buffers from the backend.

Pick-to: 6.12
Change-Id: I4fba49217052254b913ccfa6531a249fa778beb6
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
commit500be37f3e91a73c9cc2d21e8914c374a3d06b08
parente6cfa747f44903f8d9b686fcfe9b7509b3a3387d
authorTim Blechmann <tim.blechmann@qt.io>
committerTim Blechmann <tim.blechmann@qt.io>
commit timeWed, 21 Oct 2026 09:58:58 +0000