Add border-radius sizes to small and large .form-selects (#34853)

Fixes #34852

Co-authored-by: Dominik Crha <crha@havit.cz>
Co-authored-by: XhmikosR <xhmikosr@gmail.com>
Co-authored-by: Mark Otto <markd.otto@gmail.com>

scss/_variables.scss

@@ -972,7 +972,7 @@ $form-select-feedback-icon-size:        $input-height-inner-half $input-height-i
 
 $form-select-border-width:        $input-border-width !default;
 $form-select-border-color:        $input-border-color !default;
-$form-select-border-radius:       $border-radius !default;
+$form-select-border-radius:       $input-border-radius !default;
 $form-select-box-shadow:          $box-shadow-inset !default;
 
 $form-select-focus-border-color:  $input-focus-border-color !default;
@@ -982,10 +982,12 @@ $form-select-focus-box-shadow:    0 0 0 $form-select-focus-width $input-btn-focu
 $form-select-padding-y-sm:        $input-padding-y-sm !default;
 $form-select-padding-x-sm:        $input-padding-x-sm !default;
 $form-select-font-size-sm:        $input-font-size-sm !default;
+$form-select-border-radius-sm:    $input-border-radius-sm !default;
 
 $form-select-padding-y-lg:        $input-padding-y-lg !default;
 $form-select-padding-x-lg:        $input-padding-x-lg !default;
 $form-select-font-size-lg:        $input-font-size-lg !default;
+$form-select-border-radius-lg:    $input-border-radius-lg !default;
 
 $form-select-transition:          $input-transition !default;
 // scss-docs-end form-select-variables

scss/forms/_form-select.scss

@@ -60,11 +60,13 @@
   padding-bottom: $form-select-padding-y-sm;
   padding-left: $form-select-padding-x-sm;
   @include font-size($form-select-font-size-sm);
+  @include border-radius($form-select-border-radius-sm);
 }
 
 .form-select-lg {
   padding-top: $form-select-padding-y-lg;
   padding-bottom: $form-select-padding-y-lg;
   padding-left: $form-select-padding-x-lg;
   @include font-size($form-select-font-size-lg);
+  @include border-radius($form-select-border-radius-lg);
 }