fix(material/select): wrong transform origin when opening upwards inside another overlay (angular#33032)

`mat-select` had an overly-broad `:not` selector for the base case where the dropdown opens downwards that was being overwritten when opening upwards if the select is placed inside another overlay.

Fixes angular#33028.

(cherry picked from commit ab21f78)

Author: crisbeto

src/material/select/select.scss

@@ -151,35 +151,29 @@ div.mat-mdc-select-panel {
 // DOM for the Gmat versions to work. We need to bump up the specificity here
 // so that it's higher than MDC's styles.
 div.mat-mdc-select-panel {
+  $border-radius: 4px;
   width: 100%; // Ensures that the panel matches the overlay width.
   max-height: $mat-select-panel-max-height;
   outline: 0;
   overflow: auto;
   padding: 8px 0;
-  border-radius: 4px;
   box-sizing: border-box;
+  transform-origin: top center;
+  border-radius: 0 0 $border-radius $border-radius;
 
   // Necessary so the `offsetParent` of the nested `mat-option` is the
   // panel which is required for scroll calculations (see #30974).
   position: relative;
-
   background-color: token-utils.slot(select-panel-background-color, $fallbacks);
 
-  @include cdk.high-contrast {
-    outline: solid 1px;
-  }
-
-  .cdk-overlay-pane:not(.mat-mdc-select-panel-above) & {
-    border-top-left-radius: 0;
-    border-top-right-radius: 0;
-    transform-origin: top center;
-  }
-
   .mat-mdc-select-panel-above & {
-    border-bottom-left-radius: 0;
-    border-bottom-right-radius: 0;
+    border-radius: $border-radius $border-radius 0 0;
     transform-origin: bottom center;
   }
+
+  @include cdk.high-contrast {
+    outline: solid 1px;
+  }
 }
 
 .mat-select-panel-animations-enabled {