Fixes #12610

As I see from my research, the bug happens only in the real servlet environment, supposedly because of HttpServletResponse.sendError(), I didn't manage to reproduce it via mockMvc.
Tomcat creates a new HttpServletRequest in case error, which is related to "/error" path, which will be served by ErrorController.
Fortunately, request attributes are copied from the original request to the "/error"-related one, so we can put the ObservationView into the original request in order to extract this ObservationView from "/error"-related request and create a new parent observation with a given parent ObservationView. The last ObservationView propagates TraceContext to the new Observation so we have the same traceId.

Reproducer is here https://github.com/nkonev/trace-discrepancy-reproducer

curl -i 'http://localhost:8060/internal/profile/auth' -X GET -H 'Accept: text/plain, */*'

To check that the bug is fixed, you can run publishMavenJavaPublicationToMavenLocal in spring-security:web

./gradlew :spring-security-web:publishMavenJavaPublicationToMavenLocal --offline

or via IDE

then switch to the SNAPSHOT dependency nkonev/trace-discrepancy-reproducer@131a271

Before:

After:

UPD:
I also checked this PR with jetty and undertow, it works fine.