add ability to easily exclude health checks in spring starter

[zeitlinger]

See https://cloud-native.slack.com/archives/C014L2KCTE3/p1707812808682639?thread_ts=1707739322.848999&cid=C014L2KCTE3

Proposal for application.yaml:

otel:
  traces:
    sampler:
      experimental:
        routing:
          server:
            - attribute: http.route
              pattern: /actuator/
              sampler: always_off
            - attribute: http.route
              pattern: /get/cart
              sampler:
                name: traceidratio
                arg: 0.5

[zeitlinger]

@trask pointed out that open-telemetry/oteps#240 is defining this schema.

in the meantime, we should probably just document how spring users can configure this programatically.

[zeitlinger]

The documentation is part of open-telemetry/opentelemetry.io#4167.

Closing this issue, because I assume that the new file based config will later also be available for spring boot.