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ARROW-6911: [Java] Provide composite comparator

A composite comparator is a sub-class of VectorValueComparator that contains an array of inner comparators, with each comparator corresponding to one column for comparison. It can be used to support sort/comparison operations for VectorSchemaRoot/StructVector.

The composite comparator works like this: it first uses the first internal comparator (for the primary sort key) to compare vector values. If it gets a non-zero value, we just return it; otherwise, we use the second comparator to break the tie, and so on, until a non-zero value is produced by some internal comparator, or all internal comparators have been used.

Closes #5678 from liyafan82/fly_1016_comp and squashes the following commits:

6c0ea564b <liyafan82>  Revise test case
804a3fc2b <liyafan82>  Provide composite comparator

Authored-by: liyafan82 <fan_li_ya@foxmail.com>
Signed-off-by: Micah Kornfield <emkornfield@gmail.com>