Make Default HDR Conversion Overlayable

Make it possible for an overlay to specify that the default HDR
conversion mode should be "Match content dynamic range" instead of
"System-preferred conversion". Making the default value "Force" a
specific format isn't desirable, so this is just a bool to make the
default passthrough instead of system.

Note that this won't change the setting on a device that has booted with
a different default, even if the user hasn't set the setting.

Bug: b/318312317
Test: With overlay, FDR and "Match content dynamic range" is enabled
Change-Id: Iacd8fc68a5fea24a63c82d0e3ab7194379aea23e