Add EIP-7702 authorization signing to JsonRpcSigner (fixes #5056)

[sawirricardo]

Summary

JsonRpcSigner (and therefore BrowserProvider/injected-wallet signers) inherits the throwing default authorize() from AbstractSigner, so calling signer.authorize(...) fails with authorization not implemented for this signer. There is currently no way to sign an EIP-7702 authorization over JSON-RPC.

Fixes #5056.

Changes

• Implement authorize() on JsonRpcSigner. It populates any missing nonce/chainId, resolves the delegate address (ENS/Addressable), sends eth_signAuthorization to the backing node/injected provider, and normalizes the returned signature into an Authorization.
• Add a JSON-RPC test that mocks eth_signAuthorization and asserts the returned Authorization populates nonce/chainId, preserves the delegate address, and verifies back to the signing account via verifyAuthorization.

Notes

• The address in the AuthorizationRequest is the contract code to delegate to; the account that signs is the JsonRpcSigner address. This matches AbstractSigner.populateAuthorization and BaseWallet.authorize.
• eth_signAuthorization is the de-facto method name used by geth/reth and matches ethers eth_* JSON-RPC convention. MetaMask stable does not yet expose it; this PR unblocks every provider/node that does and gives injected wallets a concrete method to implement.

const signer = await browserProvider.getSigner();
const authorization = await signer.authorize({ address: delegateContract });
const tx = await signer.sendTransaction({
    to: target, authorizationList: [authorization ]
});

[sawirricardo]

if anyone able to test this will be really helpful