LocalExporter leaks a licence state listener

[DaveCTurner]

Today, LocalExporter removes its licenseChanged() method from the licence state listener when closed:

elasticsearch/x-pack/plugin/monitoring/src/main/java/org/elasticsearch/xpack/monitoring/exporter/local/LocalExporter.java

Line 155 in 816e6f6

licenseState.removeListener(this::licenseChanged);

However in fact this does nothing, because it involves a new Runnable that is different from the one we added earlier. The fix is fairly trivial, but writing the test for the fix has overflowed my stack of yaks so I'm spilling it out here.

[elasticmachine]

Pinging @elastic/es-core-infra

[rayz2007]

Hi! I'd like to help on this issue

[DaveCTurner]

Thanks @rayz2007, go for it.

[markquis91]

Hi @rayz2007 and @DaveCTurner is this still being worked on? If not I will take it.

[DaveCTurner]

No word from @rayz2007 so it seems not. Please go ahead @markquis91.

[jasontedor]

@rayz2007 @markquis91 thanks for your interest although we have opened a fix for this in #36308.