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ARROW-6311: [Java] Make ApproxEqualsVisitor accept DiffFunction to make it more flexible

Related to [ARROW-6311](https://issues.apache.org/jira/browse/ARROW-6311).

Currently ApproxEqualsVisitor will accept a epsilon for both float and double compare, and the difference calculation is always Math.abs(f1-f2)

For some cases like Validator it is not very suitable as:
i. it has different epsilon values for float/double
ii. it difference function is not Math.abs(f1-f2)

To resolve these, make this visitor accept both float/double epsilons and diff functions.

Closes #5155 from tianchen92/ARROW-6311 and squashes the following commits:

41a5dba34 <tianchen> ARROW-6311:  Make ApproxEqualsVisitor accept DiffFunction to make it more flexible

Authored-by: tianchen <niki.lj@alibaba-inc.com>
Signed-off-by: Pindikura Ravindra <ravindra@dremio.com>