Use chain metadata for more unit tests

[bvotteler]

Some unit test register types manually. It would be better to get them dynamically.

See this example in asset-registry tests.

And this relevant discussion on a previous PR: #429 (comment)

So, investigate ways and implement (where possible) more stable ways to set the types needed.
Additional note: Also check out how encoding tests create types using the getTypes() utility function.

[gregdhill]

We already have the static types from the chain metadata so it should be possible to build these types without an API connection. However with instant-seal now enabled (#578) running the tests is much easier and faster so we might consider just initializing the full API with dynamic types anyway.