Add a top-n range faceting example to RangeFacetsExample [LUCENE-10652]

In #11650, we modified the behavior of getTopChildren to actually return top-n ranges ordered by count. The original behavior of getTopChildren in RangeFacetsCounts was to return all ranges ordered by constructor-specified range order, and this behavior is now retained in the getAllChildren API (#11586).

Therefore, it would be helpful to add an example in RangeFacetsExample to demo this change. I replaced the original example of getTopChildren with getAllChildren, and will add an example of the current getTopChildren API soon.

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Migrated from [LUCENE-10652](https://issues.apache.org/jira/browse/LUCENE-10652) by Yuting Gan (@Yuti-G), updated Jul 18 2022
Pull requests: https://github.com/apache/lucene/pull/1035

Start in RangeFacetsExample and compare the existing getAllChildren example with the getTopChildren API described in the issue. Add an example showing top-n ranges ordered by count, and confirm the example clearly demonstrates the changed behavior.

Written by the indexing model from the issue text.