Creates a comprehensive Rust SDK for developing Envoy dynamic modules, providing high-level abstractions over the low-level C ABI. The SDK enables developers to write HTTP filters in Rust with type-safe interfaces for header manipulation, body processing, metadata access, and filter state management.

Includes support for HTTP callouts, filter scheduling across threads, and per-route configurations. Features comprehensive unit testing capabilities through mock implementations and integrates with Bazel build system for seamless compilation with Envoy.

The implementation handles memory management safely across FFI boundaries and provides ergonomic APIs for common filter operations like request/response processing and stream lifecycle management.

Signed-off-by: Aleksandr Sokolovskii <a.sokolovskii@sportradar.com>