WASM toolchain plugin APIs

Tier 1 - 10/10

• register_toolchain *
• initialize_toolchain
• detect_version_files
• parse_version_file
• define_toolchain_config
• define_docker_metadata
• prune_docker
• scaffold_docker
• sync_workspace
• sync_project

Tier 2 - 9/9

• extend_project_graph
• extend_command
• extend_task_command
• extend_task_script
• hash_task_contents
• define_requirements
• install_dependencies
• locate_dependencies_root *
• parse_lock
• parse_manifest
• setup_environment

Tier 3 - 8/8

• register_tool *
• download_prebuilt or native_install *
• unpack_archive
• locate_executables *
• load_versions *
• resolve_version *
• setup_toolchain
• teardown_toolchain