Prior to this commit, the `RestTemplate` observation instrumentation
would only record `RestClientException` and `IOException` as errors in
the observation. Other types of errors can be thrown by custom
components, such as `ResponseErrorHandler` and in this case they aren't
recorded with the observation.
Also, the current instrumentation does not create any observation scope
around the execution. While this would have a limited benefit as no
application code is executed there, developers could set up custom
components (such as, again, `ResponseErrorHandler`) that could use
contextual logging with trace ids.
This commit ensures that all `Throwable` are recorded as errors with the
observations and that an observation `Scope` is created around the
execution of the client exchange.
Fixes gh-32063
b484ab116f