Unit tests for @joystream/types

After updating types package for a new runtime by following steps in https://github.com/Joystream/joystream/issues/1835
it is not possible to know if the implementation was done correctly.

We lack is a set of unit tests with 100% coverage of the types that can read state from chain and look for warnings from the polkadot-api library that can detect if the custom defined types are defined correctly.

At one point there was a debug feature in the polkadot-js library that would display a warning in console when it detects a discrepancy between how a custom defined type gets encoded to raw bytes vs how it was read from chain

Maybe there is a way to write some rust utility that can construct the runtime types and compare their encoding with how the types library encodes them to find discrepancies.

Start by locating the @joystream/types package and its runtime type definitions. Review how the polkadot-api or polkadot-js library reads chain state and reports type warnings, then assess whether the proposed Rust utility can compare runtime and library encodings. Done should include a defined test strategy covering the types and detecting encoding discrepancies.