Autoclose TracerProvider in Spring-Boot Application

[frommeyerc]

Is your feature request related to a problem? Please describe.
According to SdkTracerProvider#close() JavaDoc this method should be called before the application is shut down in order to make sure all spans are reported. With the current spring-boot autoconfig this is not the case.

Describe the solution you'd like
While the current autoconfiguration create the SdkTracerProvider as a POJO baked into the OpenTelemetry @Bean it should become a @Bean in it's own right. This will allow the Spring-Context to call it's #close() method when the Context is destroyed.

Describe alternatives you've considered
As there seam to be no other @Beans that would do the shutdown instead I didn't see another option.

I'm already preparing a PR for this change.

[trask]

Closed by #5125