Adjust features for easier building on Windows

[Enet4]

This attempts to mitigate the build error when targeting Windows without Cargo feature changes (#432). Removing feature openjp2 from the native feature list is a breaking change, but we can offer alternative feature listings for Windows.

So instead of this:

cargo build --no-default-features --features=cli,rle,jpeg,rayon

One can instead do this:

cargo build --no-default-features --features=cli,default_windows

Or this, for the reference implementation of OpenJPEG:

cargo build --no-default-features --features=cli,default_windows,openjpeg-sys,openjpeg-sys-threads

Summary

• Add native_windows Cargo feature to dicom-transfer-syntax-registry and dicom-pixeldata
• Add default_windows Cargo feature to dicom-pixeldata
• Clarify documentation on JPEG 2000 adapter
• Add compile-time check for conflicting jpeg2k backend feature selection
• Change CI to build project on Windows instead of just checking