We get the `User-Agent` header for frontend events today, but not for backend events. This PR get the `User-Agent` header value, from the current request context, if any, and sends it along with any analytics events. [Relevant Slack sonversation](https://theappsmith.slack.com/archives/C02MUD8DNUR/p1679579820266469?thread_ts=1679496974.642199&cid=C02MUD8DNUR). Sample backend event with `userAgent`:  |
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| pom.xml | ||