* Introduce simple blockchain runtime for substrate tests.

* Remove bad files.

* Add needed wasm binaries.

* Refactoring.

- Repot files in test-runtime.
- Rename troublesome `Joiner::join` to `Joiner::and`.
- Rework `Slicable` to dedup code.

* More fixes and refactoring

* Rebuild substrate test wasm.

* Fix merge errors.

* Rename the disasterously named `to_vec` to `encode`.

Also rename `as_slice_then` to `with_encoded`.

* Tests for toy runtime.

* Fix doc nit

Re-introduce zero copy codec and add minimal polkadot client API which uses linked native runtime (#65)

* client-api type and move duty roster types to primitives

* tuple implementation for slicable

* mild cleanup of deserialization code

* stubs which handle encoding and decoding themselves

* fancier impl_stubs macro

* zero-copy slicable API

* minimal polkadot-client API

* fix WASM API generation

* move native environment stuff to substrate executor

* fix warnings and grumbles

* BlockId in client interface

* Sync fixes and tests

* Updated to latest primitives

* Updated dependencies

* Updated for new (old) primitives

* Network as workspace member

* substrate-network

* Removed obsolete file

* begin_transaction on hash

- Everything polkadot becomes polkadot-.
- Wasm (substrate) executor tests split from Wasm (Polkadot) runtime and
built independently.

No tests yet.
Wasm build still pulls in std.

Bottom half minus tests builds.