This also adds io.micrometer:micrometer-tracing-bridge-brave to the
Zipkin starter, otherwise we'd get no traces exported.
This also adds spring-boot-micrometer-tracing-test to the Zipkin test
starter.
Closes gh-47866
Polish test starter to:
- Align dependencies of starters and their -test companions
- Pull in regular starters from test starters
See gh-46356
Co-authored-by: Phillip Webb <phil.webb@broadcom.com>