added select readonly prop and updated the disabled schema field state

ui/src/scss/_form.scss

@@ -955,6 +955,7 @@ select {
     &:not(.disabled) .selected-container:hover {
         cursor: pointer;
     }
+    &.readonly,
     &.disabled {
         color: var(--txtHintColor);
         pointer-events: none;
@@ -978,6 +979,9 @@ select {
             }
         }
     }
+    &.disabled {
+        color: var(--txtDisabledColor);
+    }
 
     // dropdown
     .txt-missing {