chore: avoid flakiness of DefaultSupervisingTest

[apupier]

the 2 exhausted failure collected were not always the last two. So adapting the assertion to check in the full list the right number of exhausted failure instead of the last 2 elements.

Based on what I understand from the codebase, the order is not important (but if it the case, we need to fix something in runtime code and not the test)

Description

Note that this test was failing very often on different architecture (so usually marked with a last failure of 1)
For instance:
https://ci-builds.apache.org/job/Camel/job/Camel%20Core%20(Build%20and%20test)/job/main/475/testReport/junit/org.apache.camel.impl.engine/DefaultSupervisingRouteControllerTest/BuildAndTest___Matrix___JDK_NAME____jdk_21_latest___PLATFORM____ubuntu_avx____Test___testSupervising_2/
https://ci-builds.apache.org/job/Camel/job/Camel%20Core%20(Build%20and%20test)/job/main/471/testReport/junit/org.apache.camel.impl.engine/DefaultSupervisingRouteControllerTest/BuildAndTest___Matrix___JDK_NAME____jdk_17_latest___PLATFORM____s390x____Test___testSupervising/

Note that the improved assertion message revela the issue:

The 9th failure event must be exhausted. Current state of failure list: 
Attempt: 0, Is exhausted: falseCannot start, timestamp: 0
Attempt: 0, Is exhausted: falseCannot start, timestamp: 0
Attempt: 1, Is exhausted: falseCannot start, timestamp: 0
Attempt: 1, Is exhausted: falseCannot start, timestamp: 0
Attempt: 2, Is exhausted: falseCannot start, timestamp: 0
Attempt: 2, Is exhausted: falseCannot start, timestamp: 0
Attempt: 3, Is exhausted: falseCannot start, timestamp: 0
Attempt: 3, Is exhausted: trueCannot start, timestamp: 0
Attempt: 3, Is exhausted: falseCannot start, timestamp: 0
Attempt: 3, Is exhausted: trueCannot start, timestamp: 0 ==> expected: <true> but was: <false>

Target

• I checked that the commit is targeting the correct branch (note that Camel 3 uses camel-3.x, whereas Camel 4 uses the main branch)

Tracking

• If this is a large change, bug fix, or code improvement, I checked there is a JIRA issue filed for the change (usually before you start working on it).

Apache Camel coding standards and style

• I checked that each commit in the pull request has a meaningful subject line and body.

• I have run mvn clean install -DskipTests locally from root folder and I have committed all auto-generated changes.

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