Fix long label overflow in the sidebar

When they overflow, menu items in the sidebar have their text that
continue a few pixels beyond the position it should stop to take into
account their margin, and if the menu item contains a badge, it is not
aligned as expected.

By setting `overflow: hidden`, both problems are adressed.  For a better
visual clue of the truncation, `text-overflow: ellipsis` is combined to
the this.

Changelog: fixed

app/assets/stylesheets/framework/contextual_sidebar.scss

@@ -267,6 +267,8 @@
 
     .nav-item-name {
       flex: 1;
+      overflow: hidden;
+      text-overflow: ellipsis;
     }
 
     > a,

app/assets/stylesheets/startup/startup-dark.scss

@@ -1095,6 +1095,8 @@ input {
 }
 .nav-sidebar li .nav-item-name {
   flex: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
 }
 .nav-sidebar li > a,
 .nav-sidebar li > .fly-out-top-item-container {

app/assets/stylesheets/startup/startup-general.scss

@@ -1076,6 +1076,8 @@ input {
 }
 .nav-sidebar li .nav-item-name {
   flex: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
 }
 .nav-sidebar li > a,
 .nav-sidebar li > .fly-out-top-item-container {

ee/app/assets/stylesheets/startup/startup-dark.scss

@@ -1095,6 +1095,8 @@ input {
 }
 .nav-sidebar li .nav-item-name {
   flex: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
 }
 .nav-sidebar li > a,
 .nav-sidebar li > .fly-out-top-item-container {

ee/app/assets/stylesheets/startup/startup-general.scss

@@ -1076,6 +1076,8 @@ input {
 }
 .nav-sidebar li .nav-item-name {
   flex: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
 }
 .nav-sidebar li > a,
 .nav-sidebar li > .fly-out-top-item-container {