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GH-37893: [Java] Move Types.proto in a subfolder (#37894)



### Rationale for this change

Types.proto is a Gandiva protobuf definition used by Gandiva to exchange data between Java and C++. This file is packaged automatically within arrow-gandiva jar but because of its generic name, it may cause conflicts in others' people project.

### What changes are included in this PR?

Move `Types.proto` into `gandiva/types.proto` (also matching convention of using lowercase filename) so that it become less likely to cause a conflict.

### Are these changes tested?

Change should have no impact on the feature itself. Manually check the resulting jar to confirm that `types.proto` is not located at the root of the archive.

### Are there any user-facing changes?

No user-facing. Developers who were actually referencing Gandiva `Types.proto` in their project may have to change their `import` directive.

**This PR includes breaking changes to public APIs.**

* Closes: #37893

Authored-by: Laurent Goujon <laurent@apache.org>
Signed-off-by: David Li <li.davidm96@gmail.com>