First release candidate for go-libddwaf v5, which tracks libddwaf v2.

⚠️ Release candidate — APIs may still change before the final v5.0.0. Not recommended for production use yet.

This is a major version with breaking API changes. See the "Upgrading from v4 to v5" section of the README for the full migration guide.

Highlights

• libddwaf v2 bindings — WAFObject/WAFObjectKV are now value-type aliases over the 16-byte ddwaf_object union (no need to import internal/bindings).
• Reworked encoding API — MapBuilder/ArrayBuilder, typed slice/map fast paths, a Truncations value type, and an Encoder helper for Encodable implementers.
• Ephemeral evaluation via Context.NewSubcontext() → *Subcontext; RunAddressData now has a single Data field (no more Persistent/Ephemeral).
• Context-aware API — Handle.NewContext, Context.Run, and Context.NewSubcontext take a context.Context; Builder.Build() returns (*Handle, error).
• NewBuilder() no longer takes obfuscator regexes (configure via AddOrUpdateConfig(..., "obfuscator/config", ...)).
• Concurrency — per-instance pinner-lifetime fix for concurrent Run/Close; race-detector clean.

Merged in #215.