Refactor package structure to com.digitalpetri.util.byteops

[kevinherron]

What problem(s) was I solving?

The package structure was flat, with all classes in com.digitalpetri.util. This made it unclear which module each class belonged to and didn't follow Java conventions for library organization.

What user-facing changes did I ship?

Breaking Change: Package names have been updated across all modules:

Module	Old Package	New Package
byteops (core)	com.digitalpetri.util	com.digitalpetri.util.byteops
byteops-netty	com.digitalpetri.util	com.digitalpetri.util.byteops.netty
byteops-unsigned	com.digitalpetri.util	com.digitalpetri.util.byteops.unsigned

Users will need to update their import statements when upgrading.

How I implemented it

• Moved all source files to new package directories matching the module structure
• Updated package declarations in all Java files
• Added explicit imports where classes now reference types from other packages
• Made AbstractByteOpsTest public so it can be extended from test classes in other modules

How to verify it

Manual Testing

• All tests pass (mvn clean test)

Description for the changelog

Reorganize package structure to com.digitalpetri.util.byteops with module-specific subpackages (netty, unsigned). This is a breaking change requiring import updates.