[ESQL] Update inline docs for 8.15 (#186835)

Aggregations, operators, and commands still need to be added manually

- `::` is the only one so far landing in 8.15.0

---------

Co-authored-by: Stratoula Kalafateli <efstratia.kalafateli@elastic.co>

packages/kbn-text-based-editor/src/esql_documentation_sections.tsx

@@ -4456,6 +4456,33 @@ The following boolean operators are supported:
         />
       ),
     },
+    {
+      label: i18n.translate(
+        'textBasedEditor.query.textBasedLanguagesEditor.documentationESQL.castOperator',
+        {
+          defaultMessage: 'Cast (::)',
+        }
+      ),
+      description: (
+        <Markdown
+          markdownContent={i18n.translate(
+            'textBasedEditor.query.textBasedLanguagesEditor.documentationESQL.castOperator.markdown',
+            {
+              defaultMessage: `### CAST (\`::\`)
+The \`::\` operator provides a convenient alternative syntax to the \`TO_<type>\` type conversion functions.
+
+Example:
+\`\`\`
+ROW ver = CONCAT(("0"::INT + 1)::STRING, ".2.3")::VERSION
+\`\`\`
+              `,
+              description:
+                'Text is in markdown. Do not translate function names, special characters, or field names like sum(bytes)',
+            }
+          )}
+        />
+      ),
+    },
     {
       label: i18n.translate(
         'textBasedEditor.query.textBasedLanguagesEditor.documentationESQL.inOperator',