JapaneseNumberFilter does not take whitespaces into account when concatenating numbers [LUCENE-8959]

Today the JapaneseNumberFilter tries to concatenate numbers even if they are separated by whitespaces. So for instance "10 100" is rewritten into "10100" ~~even if the tokenizer doesn't discard punctuations~~. In practice this is not an issue but this can lead to giant number of tokens if there are a lot of numbers separated by spaces. The number of concatenation should be configurable with a sane default limit in order to avoid creating giant tokens that slows down the analysis if the tokenizer is not correctly configured.

---
Migrated from [LUCENE-8959](https://issues.apache.org/jira/browse/LUCENE-8959) by Jim Ferenczi (@jimczi)

Start with JapaneseNumberFilter and reproduce the reported "10 100" behavior using numbers separated by whitespace. Determine how concatenation currently proceeds and define a configurable limit with a sensible default; done means separated numbers no longer produce unbounded giant tokens while normal concatenation remains covered by tests.

Written by the indexing model from the issue text.