Fix xpack.usage ILM actions

[pquentin]

I've been trying to understand today why sometimes 2 responses for xpack.usage validate, and sometimes only one. I don't understand it yet, but I have fixed the Type 'string[]' has no properties in common with type 'IlmActions'. issue. Before/after:

$ make validate api=xpack.usage branch=main | rg --fixed-strings "Type 'string[]' has no properties in common with type 'IlmActions'." | wc -l
    3468
$ git checkout xpack-usage-ilm-action
Switched to branch 'xpack-usage-ilm-action'
$ make validate api=xpack.usage branch=main | rg --fixed-strings "Type 'string[]' has no properties in common with type 'IlmActions'." | wc -l
       0

(Plenty of other issues remain, like configurations is totally missing even though it encodes a lot of information since Elasticsearch 7.15.

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
ilm.delete_lifecycle	🟢	2/2	2/2
ilm.explain_lifecycle	🟢	5/5	5/5
ilm.get_lifecycle	🟢	8/8	8/8
ilm.get_status	🟢	4/4	4/4
ilm.migrate_to_data_tiers	⚪	Missing test	Missing test
ilm.move_to_step	⚪	Missing test	Missing test
ilm.put_lifecycle	🟢	6/6	6/6
ilm.remove_policy	🟢	5/5	5/5
ilm.retry	⚪	Missing test	Missing test
ilm.start	⚪	Missing test	Missing test
ilm.stop	🟢	4/4	4/4
xpack.usage	🔴	40/40	2/36

You can validate these APIs yourself by using the make validate target.

[pquentin]

It turns out ILM and Xpack usage output different representations for min_age. It's always a TimeValue, but:

• ILM APIs call getStringRep() which outputs units for all non-negative values
• XPack usage calls getMillis() which returns a long which is why I'm using DurationValue<UnitMillis> now.

[pquentin]

https://github.com/elastic/elasticsearch/blob/b4e852a54be436d8b8036da0a0ec4a472d44524a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleFeatureSetUsage.java#L190