Set related children's thumbnail to default 4

[wangf1122]

Set a limit to rendering the number of children thumbnail. Similar to the card view

core-geonetwork/web-ui/src/main/resources/catalog/views/default/templates/recordView/type-dataset.html

Line 121 in ed27371

data-size="4"

In some extreme case, the user can set hundreds of children to a parent record and causing some mess to the parent record view page. This issue is discussed in pull request of #8608

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[davidblasby]

looking at the page @fxprunayre indicated (https://sdi.eea.europa.eu/catalogue/srv/eng/catalog.search#/metadata/3c362237-daa4-45e2-8c16-aaadfb1a003b).

I see about 133 graphic overview requests - totally about 8mb. Total page load time was 5 seconds. The page was mostly visible after a bit more than 1 seconds.

Based on this, I would expect that setting this to higher than 4 would be fine. Even considering base64 encoding, this would increase the size of the document by 10.5mb (for 133 overviews).

cf. #8608