* core: check for sessionLockSurface before calling render
This is needed, because when a new monitor is added via `onGlobal` the
order of the events is not guaranteed. Meaning that render for a
particular monitor might get called before a `CSessionLockSurface` for
that monitor exists.
* renderer: remove widgets for destroyed lockSurfaces
* asyncResourceGatherer: don't create duplicate dma frames for a specific stringPort
* core: remove renderer widgets in ~CSessionLockSurface instead of in onGlobalRemoved
* Revert "core: remove renderer widgets in ~CSessionLockSurface instead of in onGlobalRemoved"
This reverts commit 405aa42de8.
Because of destruction order, it is safer to do it in `onGlobalRemoved`.
* core: ditch dynamic DMAFrame generation
* core: identify DMAFrames via output size and stringPort
* core: fallback to background color for dynamic outputs with background:path=screenshot
* core: remove output pointer from DMAFrame
