WIP: POC static-dynamic bridge

• package pybind with conan
• integrate pybind to project
• add py directory to pylene (type-erased machinery)
• add pybind directory to root (actual python bindings)
• write cpp unit test
• integrate a mechanism to run python unit test
• write python unit test to test compiled bindings
• add a type-erased span (any_span)
• add a mechanism to expose a buffer to numpy so that they can be tested through python unit tests

@Moxyze for ref

fixes #61 (closed)