Fix Incomplete string escaping or encoding (elastic#212847)

Fix for
[https://github.com/elastic/kibana/security/code-scanning/546](https://github.com/elastic/kibana/security/code-scanning/546)

To fix the problem, we need to ensure that backslashes are also escaped
in the `trim_key` and `trim_value` properties of the `kvInput` object.
This can be done by adding an additional replace call to escape
backslashes before escaping single and double quotes. The best way to
fix this without changing existing functionality is to use a regular
expression with the `g` flag to replace all occurrences of backslashes
with double backslashes.

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
(cherry picked from commit 8970b99)

x-pack/platform/plugins/shared/integration_assistant/server/util/processors.ts

@@ -70,11 +70,11 @@ export function createKVProcessor(kvInput: KVProcessor, state: KVState): ESProce
   });
   const template = env.getTemplate('kv.yml.njk');
   if (kvInput.trim_key) {
-    kvInput.trim_key = kvInput.trim_key.replace(/['"]/g, '\\$&');
+    kvInput.trim_key = kvInput.trim_key.replace(/\\/g, '\\\\').replace(/['"]/g, '\\$&');
   }
 
   if (kvInput.trim_value) {
-    kvInput.trim_value = kvInput.trim_value.replace(/['"]/g, '\\$&');
+    kvInput.trim_value = kvInput.trim_value.replace(/\\/g, '\\\\').replace(/['"]/g, '\\$&');
   }
   const renderedTemplate = template.render({
     kvInput,