Add namespace label selector

[W1seKappa]

Description

Added namespace label selector for filtering pods in the DefaultEvictor plugin.
This pull request was created to finalize the initiative from that pr1501

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• ✅ login: W1seKappa / name: Danila Bobkov (37d0977, 66c86f8)

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[W1seKappa]

@ingvagabund Hi, I'm happy to continue the discussion based on the initiative from this pr1501.

[ingvagabund]

I understand the idea here. If a namespace is matched by the label selector it's returned. If it is not an empty list is returned. I.e.:

• indexer.ByIndex(indexName, NSmatched) -> {NSmatched} // list with a single ns
• indexer.ByIndex(indexName, NSNotmatched) -> {} // empty list

On the other hand getNamespacesListByLabelSelector gives the belief all namespaces matching a label selector are returned. I.e. a label selector is the key, not a namespace. I.e.

• indexer.ByIndex(indexName, LS1) -> list of namespaces matching LS1
• ...
• indexer.ByIndex(indexName, LSN) -> list of namespaces matching LSN

Given each profile can have its own DefaultEvictor configuration with a different label selector the current global "namespaceWithLabelSelector" indexer will not work correctly as once the first indexer gets registered, any second attempt returns the first indexer. So the second label selector will get ignored and all DefaultEvictors will share the first label selector.

[ingvagabund]

@W1seKappa thank you for taking over. As the next step I suggest to create another unit test that have two profiles configured. Each with a different label selector and to make sure both evictors evict distinct set of namespaces to correctly validate the functionality. There's no need to create actual profiles. Just mimicking it through creating two default evictors over the same namespace informer.