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ARROW-6853: [Java] Support vector and dictionary encoder use different hasher for calculating hashCode

Related to [ARROW-6853](https://issues.apache.org/jira/browse/ARROW-6853).

Hasher interface was introduce in ARROW-5898 and now have two different implementations (MurmurHasher and SimpleHasher) and it could be more in the future.

And currently ValueVector#hashCode and DictionaryHashTable only use SimpleHasher for calculating hashCode. This issue enables them to use different hasher or even user-defined hasher for their own use cases.

Closes #5625 from tianchen92/ARROW-6853 and squashes the following commits:

2e0e4c9c4 <tianchen> fix style
fffb4ac05 <tianchen> ARROW-XXXX:  Support vector and dictionary encoder use different hasher for calculating hashCode

Authored-by: tianchen <niki.lj@alibaba-inc.com>
Signed-off-by: Micah Kornfield <emkornfield@gmail.com>