Add support for javalin 5, currently the instrumentation crashes

[JonasKunz]

Per report in the discussion forums our instrumentation currently doesn't support javalin 5:

java.lang.IncompatibleClassChangeError: Found interface io.javalin.http.Context, but class was expected
  at co.elastic.apm.agent.javalin.JavalinInstrumentation$HandlerAdapterAdvice.setSpanAndTransactionName(JavalinInstrumentation.java:177) ~[elastic-apm-agent.jar:1.52.1]
  at xx.xxxxx.xxxxxx.xxxxxxx.xxxxx.TestFilter.handle(TestFilter.java:40) ~[test-1.0.0-SNAPSHOT.jar:?]
  at io.javalin.router.Endpoint.handle(Endpoint.kt:52) ~[javalin-6.1.3.jar:6.1.3]
  at io.javalin.router.ParsedEndpoint.handle(ParsedEndpoint.kt:15) ~[javalin-6.1.3.jar:6.1.3]

We should

• add support for javalin 5
• Ensure that version 3.13.8, latest 3.x, latest 4.x and overall latest (currently 5.x) still work via tests (see this as an example)
• Add javalin to the dependabot config to ensure we don't miss future updates