Shape Python language runtime extension.
Provides a shape.language_runtime capability that embeds CPython
for executing foreign "python" { ... } blocks in Shape programs.
ABI Exports
All C ABI exports (shape_plugin_info, shape_abi_version,
shape_capability_manifest, shape_capability_vtable,
shape_language_runtime_vtable) are generated by the
[shape_abi_v1::language_runtime_plugin!] macro below.