Merge signAllTransactions improvements into solana-wallet-adapter codebase

[zpalmtree]

Hey guys, would love to use signAllTransactions in the solana-wallet-adapter - https://github.com/anza-xyz/wallet-adapter - I see you added it to this repo a few months ago.

The walletconnect adapter there seems a fair few commits behind this repo - https://github.com/anza-xyz/wallet-adapter/tree/master/packages/wallets/walletconnect

I tried to merge in this codebase manually and I sorta got it working but doesn't seem like the UI elements are fully finished.