Improve metadata load time

[jordy25519]

metadata instantiation process is quite slow for dapps > 5 seconds.
can view this as a design issue as to why eager loading all the metadata when connecting is necessary or an optimization issue
i.e. should a dapp only load the system types and the the specifics it wants to use vs. all types, docs, etc.

[jordy25519]

maybe rust/wasm bindings to this can help with decoding: https://github.com/ascjones/subsee/blob/master/src/main.rs