Bump to latest scale-encode/decode/value and fix test running

[jsdw]

Running tests locally failed because we were still explicitly passing incorrect paths, so I fixed that. I also bumped versions of scale-encode, scale-decode and scale-value and fixed anything that broke as a result, and changed the CI to download to substrate-node to mirror the changed binary name.

One change that was spotted here in a failing test: previously, scale_value::Value's would each come with a type ID of the type they decoded from, and this could be used to re-encode the value in the same way. This is no longer always possible, because we now "skip" over Compact types when decoding. It's a trade-off:

• Previously, any compact encoded thing (value, struct, whatever) was decoded to a single number. This lost information about the structs etc on the way there, and decoding into matching structs would fail because of this.
• Now, we preserve all of the struct (composite) types in the decoding, but there's no longer a sensible place for the "compact" type ID to live (each decoded struct etc has its own type ID).

I think this is fair enough; the Type IDs that are attached to values are meant to help with diagnostics and such more than anything, and values should be encoded, as other types, by providing a target type ID to aim them at.