MDL-69703 theme_boost: ensure multi-select options take all space.

theme/boost/scss/moodle/forms.scss

@@ -342,6 +342,9 @@ select.form-control {
     &[size],
     &[multiple] {
         padding-right: 0;
+        option {
+            width: fit-content;
+        }
     }
 }
 

theme/boost/style/moodle.css

@@ -16655,6 +16655,8 @@ fieldset.coursesearchbox label {
 
 select.form-control[size], select.form-control[multiple] {
   padding-right: 0; }
+  select.form-control[size] option, select.form-control[multiple] option {
+    width: fit-content; }
 
 /* Non-bootstrap selects with a size show their contents outside of the element.
  * Remove when we update to stable bootstrap 4. (MDL-56511) */

theme/classic/style/moodle.css

@@ -16889,6 +16889,8 @@ fieldset.coursesearchbox label {
 
 select.form-control[size], select.form-control[multiple] {
   padding-right: 0; }
+  select.form-control[size] option, select.form-control[multiple] option {
+    width: fit-content; }
 
 /* Non-bootstrap selects with a size show their contents outside of the element.
  * Remove when we update to stable bootstrap 4. (MDL-56511) */