Support the EIP-5792 methods:

• wallet_sendCalls
• wallet_getCallsStatus
• wallet_getCapabilities

Specifically:

• Modularise new method support into separate files under src/methods.
  • As opposed to continually extending src/wallet.ts.
• Use @metamask/superstruct to easily validate request parameters against a schema / struct.
• Move common validation functions to new src/validation.ts.
• Export new types inferred from structs.
  • Specifically as opposed to * for easier API diffs.

An additional benefit of using @metamask/superstruct is including multiple validation errors within a single RPC error:

Error: Invalid params

0 > from - Expected a string matching \`/^0x[0-9a-fA-F]{40}$/\` but received "123"
0 > chainId - Expected a string, but received: 123
0 > calls - Expected an array value, but received: "123"