### CI Link

https://gradle-enterprise.elastic.co/s/dvtf7swsnm44o

### Repro line

./gradlew ':x-pack:plugin:autoscaling:test' --tests "org.elasticsearch.xpack.autoscaling.capacity.AutoscalingCalculateCapacityServiceTests.testContext" -Dtests.seed=15E8E10F966ECA7A -Dtests.locale=be-BY -Dtests.timezone=America/Noronha -Druntime.java=17	

### Does it reproduce?

Yes

### Applicable branches

main

### Failure history

https://gradle-enterprise.elastic.co/scans/tests?search.timeZoneId=Europe/Rome&tests.container=org.elasticsearch.xpack.autoscaling.capacity.AutoscalingCalculateCapacityServiceTests&tests.test=testContext

### Failure excerpt

```
org.elasticsearch.xpack.autoscaling.capacity.AutoscalingCalculateCapacityServiceTests > testContext FAILED
    java.lang.NullPointerException: Cannot invoke "org.elasticsearch.xpack.autoscaling.capacity.AutoscalingCapacity.node()" because the return value of "org.elasticsearch.xpack.autoscaling.capacity.AutoscalingDeciderContext.currentCapacity()" is null
        at __randomizedtesting.SeedInfo.seed([EB0EF2643F2D6C41:7D3B02C92A094B8F]:0)
        at org.elasticsearch.xpack.autoscaling.capacity.AutoscalingCalculateCapacityServiceTests.testContext(AutoscalingCalculateCapacityServiceTests.java:225)
```
x-pack/plugin/autoscaling/src/test/java/org/elasticsearch/xpack/autoscaling/capacity/AutoscalingCalculateCapacityServiceTests.java
IllegalArgumentException exception = expectThrows(IllegalArgumentException.class, () -> service.validate(policy));
        assertThat(
            exception.getMessage(),
            equalTo("decider [" + FixedAutoscalingDeciderService.NAME + "] not applicable to policy with roles [ " + badRoles + "]")
        );
    }
    public void testValidateNotEmptyDeciders() {
        AutoscalingCalculateCapacityService service = new AutoscalingCalculateCapacityService(Set.of(new FixedAutoscalingDeciderService()));
        String policyName = randomAlphaOfLength(8);
        AutoscalingPolicy policy = new AutoscalingPolicy(
            policyName,
            new TreeSet<>(randomBoolean() ? Set.of() : Set.of("master")),
            new TreeMap<>()
        );
        IllegalArgumentException exception = expectThrows(IllegalArgumentException.class, () -> service.validate(policy));
        assertThat(
            exception.getMessage(),
            equalTo("no default nor user configured deciders for policy [" + policyName + "] with roles [" + policy.roles() + "]")
        );
    }
    public void testValidateSettingName() {
        AutoscalingCalculateCapacityService service = new AutoscalingCalculateCapacityService(Set.of(new FixedAutoscalingDeciderService()));
        Set<String> legalNames = Set.of(
            FixedAutoscalingDeciderService.STORAGE.getKey(),
            FixedAutoscalingDeciderService.MEMORY.getKey(),
            FixedAutoscalingDeciderService.NODES.getKey()
        );
        String badSettingName = randomValueOtherThanMany(legalNames::contains, () -> randomAlphaOfLength(8));
        AutoscalingPolicy policy = new AutoscalingPolicy(
            randomAlphaOfLength(8),