[8.15] [Canvas] Fix unescaped backslashes (#196311) (#196428)

# Backport

This will backport the following commits from `main` to `8.15`:
- [[Canvas] Fix unescaped backslashes
(#196311)](#196311)

<!--- Backport version: 9.4.3 -->

### Questions ?
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Fix unescaped backslashes (#196311)\n\nFixes unescaped backslashes in
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Fix unescaped backslashes (#196311)\n\nFixes unescaped backslashes in
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Fix unescaped backslashes (#196311)\n\nFixes unescaped backslashes in
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BACKPORT-->

Co-authored-by: Nick Peihl <[email protected]>

src/plugins/presentation_util/public/components/expression_input/autocomplete.ts

@@ -438,7 +438,7 @@ function maybeQuote(value: any) {
     if (value.match(/^\{.*\}$/)) {
       return value;
     }
-    return `"${value.replace(/"/g, '\\"')}"`;
+    return `"${value.replace(/[\\"]/g, '\\$&')}"`;
   }
   return value;
 }