Improve control char rendering and escape button styling (#37094)

Follow-up to #37078.

- Use Unicode Control Pictures](U+2400-U+2421) to render C0 control characters
- Make it work in diff view too
- Replace escape warning emoji with SVG
- Align escape warning button with code lines

---------

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

web_src/css/review.css

@@ -15,11 +15,20 @@
   transform: scale(1.1);
 }
 
+.lines-escape .toggle-escape-button {
+  margin: -1px 2px 0;
+}
+
 .lines-escape .toggle-escape-button::before {
-  visibility: visible;
-  content: "⚠️";
-  font-family: var(--fonts-emoji);
-  color: var(--color-red);
+  content: "";
+  display: inline-flex;
+  width: 14px;
+  height: 14px;
+  background-color: var(--color-yellow); /* TODO: maybe it needs a new kind of color, there is no suitable "warning" color in the current palette */
+  mask-image: var(--octicon-alert-fill);
+  -webkit-mask-image: var(--octicon-alert-fill);
+  mask-size: contain;
+  -webkit-mask-size: contain;
 }
 
 .repository .diff-file-box .code-diff td.lines-escape {