This is necessary because one of the current errors when building
the test service boils down to:

the trait bound `polkadot_test_runtime::RuntimeApiImpl<...>`:
  `polkadot_primitives::v1::ParachainHost<...>` is not satisfied

This is WIP because it appears to be causing some std leakage into
the wasm environment, or something; the compiler is currently
complaining about duplicate definitions of `panic_handler` and `oom`.
Presumably I have to identify all std types (Vec etc) and replace
them with sp_std equivalents.