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ARROW-12378: [C++][Gandiva] Implement castVARBINARY functions

Implement the following functions:

- castVARBINARY(varchar, len)
- castVARBINARY(varbinary, len)
- castVARBINARY(float/double/int/bigint, bigint len)

Closes #10023 from jpedroantunes/feature/add-cast-varbinary and squashes the following commits:

51173737e <João Pedro> Add base implementation for castVARBINARY methods and the respective tests

Authored-by: João Pedro <joaop@simbioseventures.com>
Signed-off-by: Praveen <praveen@dremio.com>