Update subxt and substrate dependencies

[ascjones]

Closes #1064

Compatible with https://github.com/paritytech/substrate-contracts-node/releases/tag/v0.27.0

[ascjones]

Depends on new substrate-contracts-node release paritytech/substrate-contracts-node#192

Blocked on updating substrate-contracts-node to polkadot-v0.9.43, which in fact contains the updated ContractResult<R, Balance, EventRecord> with the EventRecord parameter type.

[JoshOrndorff]

I see that the contracts_runtime.scale file changed in this PR. How often does that happen? And how to you generate that file?

If I want to make cargo contract work with my chain that uses AccountId20 do I need to generate a similar file from my own runtime?

I've also asked about this in https://substrate.stackexchange.com/q/9055/372

EDIT: I've at least figured out how to generate the file now from https://docs.rs/subxt/0.29.0/subxt/attr.subxt.html#metadata

I'm still not totally clear on when and whether i need to regenerate it, but I'm experimenting now. My guess is that AccountId is a sufficiently important change that I'll need to regenerate it.