Clone button enhancements (#33362)

- Add box-shadow to default tippy theme
- Make colors for tabs match the ones from `.ui.tabular.menu`
- Remove tippy arrow and slightly offset tooltip closer to the button
- Fix setting of `aria-haspopup` when default role is used with tippy

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/css/repo.css

@@ -1630,7 +1630,7 @@ td .commit-summary {
 }
 
 .repo-button-row-left {
-  flex: 1;
+  flex-grow: 1;
 }
 
 .repo-button-row .button {