Add Spring Boot Smoke Test

[willarmiros]

Spring Boot packages its apps in a unique way, and loads dependencies using a custom ClassLoader that makes them invisble to the System Class Loader which the agent uses at premain to discover useful dependencies like Trace ID injection libraries. More generally, we've had issues specific to spring boot in the past and should have a way to smoke test Spring Boot apps.

See OTel Java Instrumentation Spring Boot smoke tests for reference: https://github.com/open-telemetry/opentelemetry-java-instrumentation/tree/67371ecfc9fc9b4cf7985ae96ffc5bde9a246b11/smoke-tests/springboot