Feat/no more weird runtime api encoding

[camfairchild]

Description

This PR changes the runtime APIs to only use the actual types they are expecting, instead of encoding/decoding to Vec<u8>.
This means we can decode runtime API results using just the chain metadata, so we can more easily support future changes to the APIs.
This breaks old clients, but the timing with RAO makes it worthwhile, as old clients will break anyway.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

Clients upgrading should be grabbing their type information from the V15 Metadata on the chain.
They should also be able to see these runtime APIs listed there, with their expected input and output types, and the encoding for said types.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules