Build kuromoji system dictionary as a separated jar and load it from JapaneseTokenizer at runtime [LUCENE-8869]

This is a sub-task for #9860.
In this issue, I will try to make small but self-contained changes to kuromoji system dictionary.
- Make it possible to build a jar that contains (maybe) only dictionary data resource generated by the `build-dict` task.
- Maybe a new ant target will be added.
- Make it possible to load external dictionary when initializing JapaneseTokenizer.
- Some work are already done on #9906
- Decouple current system dictionary data (mecab ipadic) from kuromoji itself and use it as default (Possibly it can be done with another issue).

Also, some refactoring of the directory/source tree structure may be needed.

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Migrated from [LUCENE-8869](https://issues.apache.org/jira/browse/LUCENE-8869) by Tomoko Uchida (@mocobeta), 1 vote, updated Jun 23 2019
Linked issues:
- #9860

Start by reading the parent issue #9860 and related work in #9906, then inspect the kuromoji `build-dict` task and `JapaneseTokenizer` initialization. The scope includes a separate dictionary-data jar, runtime loading of an external dictionary, and possible source-tree refactoring; confirm which parts remain before defining completion.

Written by the indexing model from the issue text.