refactor: use generics on chain queries

[rflechtner]

fixes KILTProtocol/ticket#305

This adds generics to polkadot api calls for chain queries, which communicates the expected return type to our typescript code. It also removes the custom QueryResult type as a return type for chain queries which included null and undefined, which was simply not correct - queries will always return Codec types.

This also implements type checks at runtime for codec types provided to decoder methods, making sure that they are only used in appropriate contexts.

How to test:

Run integration tests with mashnet-node v 0.22 and a develop version

Checklist:

• I have verified that the code works
• I have verified that the code is easy to understand
  • If not, I have left a well-balanced amount of inline comments
• I have left the code in a better state
• I have documented the changes (where applicable)

[rflechtner]

Timo requested I open this for review and implement type checks on a separate ticket: https://github.com/KILTprotocol/ticket/issues/486

[wischli]

I guess you already know that some stuff like the RootDelegationRecord or DelegationNodeRecord breaks stuff in the tests. Besides that, almost all of my complaints are towards the documentation (and really minor).

[wischli]

One tests needs fixing. Other than that, minor stuff.

[wischli]

LGTM