Camera-specific hwaccel settings for timelapse exports (correct base) (#21386)

* added hwaccel_args to camera.record.export config struct

* populate camera.record.export.hwaccel_args with a cascade up to camera then global if 'auto'

* use new hwaccel args in export

* added documentation for camera-specific hwaccel export

* fix c/p error

* missed an import

* fleshed out the docs and comments a bit

* ruff lint

* separated out the tips in the doc

* fix documentation

* fix and simplify reference config doc

frigate/config/camera/record.py

@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Optional
+from typing import Optional, Union
 
 from pydantic import Field
 
@@ -70,6 +70,9 @@ class RecordExportConfig(FrigateBaseModel):
     timelapse_args: str = Field(
         default=DEFAULT_TIME_LAPSE_FFMPEG_ARGS, title="Timelapse Args"
     )
+    hwaccel_args: Union[str, list[str]] = Field(
+        default="auto", title="Export-specific FFmpeg hardware acceleration arguments."
+    )
 
 
 class RecordConfig(FrigateBaseModel):