Always render the Annotation- and XFA-layers with light color-scheme (issue 19871)

The intention with PR 19819 was to change how colours are specified for the viewer UI, however it wasn't intended to affect elements in the Annotation- and XFA-layers.
Hence we enforce the light `color-scheme` for these layers, and also make sure to provide a default `color` for PopupAnnotations.

Author: Snuffleupagus

web/annotation_layer_builder.css

@@ -14,6 +14,8 @@
  */
 
 .annotationLayer {
+  color-scheme: only light;
+
   --annotation-unfocused-field-background: url("data:image/svg+xml;charset=UTF-8,<svg width='1px' height='1px' xmlns='http://www.w3.org/2000/svg'><rect width='100%' height='100%' style='fill:rgba(0, 54, 255, 0.13);'/></svg>");
   --input-focus-border-color: Highlight;
   --input-focus-outline: 1px solid Canvas;
@@ -305,6 +307,7 @@
 
   .popup {
     background-color: rgb(255 255 153);
+    color: black;
     box-shadow: 0 calc(2px * var(--total-scale-factor))
       calc(5px * var(--total-scale-factor)) rgb(136 136 136);
     border-radius: calc(2px * var(--total-scale-factor));

web/xfa_layer_builder.css

@@ -28,6 +28,8 @@
 }
 
 .xfaLayer {
+  color-scheme: only light;
+
   background-color: transparent;
 }