fix(VOverlay): don't inherit scrim opacity

fixes #20969

Author: KaelWD

packages/vuetify/src/components/VOverlay/VOverlay.sass

@@ -26,6 +26,7 @@
       height: 100%
 
   .v-overlay
+    --v-overlay-opacity: #{$overlay-opacity}
     border-radius: inherit
     display: flex
     left: 0
@@ -48,7 +49,7 @@
     border-radius: inherit
     bottom: 0
     left: 0
-    opacity: $overlay-opacity
+    opacity: var(--v-overlay-opacity)
     position: fixed
     right: 0
     top: 0

packages/vuetify/src/components/VOverlay/_variables.scss

@@ -1,3 +1,3 @@
 // Defaults
-$overlay-opacity: var(--v-overlay-opacity, 0.32) !default;
+$overlay-opacity: 0.32 !default;
 $overlay-scrim-background: rgb(var(--v-theme-on-surface)) !default;