Change review buttons to icons to make space for text (#20934)

The layout on the review code view was broken depending on length of the text. Change all three buttons to icons with tooltip to make more space for these long texts.

Fixes: #20922

web_src/svg/gitea-join.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16"><path d="M14 10.9V8.75h1.25a.75.75 0 0 0 0-1.5H14V5.1a.25.25 0 0 0-.43-.17l-2.9 2.9a.25.25 0 0 0 0 .35l2.9 2.9a.25.25 0 0 0 .43-.18ZM.75 8.75a.75.75 0 0 1 0-1.5H2V5.1a.25.25 0 0 1 .43-.17l2.9 2.9a.25.25 0 0 1 0 .35l-2.9 2.9A.25.25 0 0 1 2 10.9V8.75Zm6.5-6.5a.75.75 0 0 0 1.5 0v-.5a.75.75 0 0 0-1.5 0zM8 6a.75.75 0 0 1-.75-.75v-.5a.75.75 0 0 1 1.5 0v.5A.75.75 0 0 1 8 6Zm-.75 2.25a.75.75 0 0 0 1.5 0v-.5a.75.75 0 0 0-1.5 0zM8 12a.75.75 0 0 1-.75-.75v-.5a.75.75 0 0 1 1.5 0v.5A.75.75 0 0 1 8 12Zm-.75 2.25a.75.75 0 0 0 1.5 0v-.5a.75.75 0 0 0-1.5 0z"/></svg>