feat(keysets): init keyset

[Ansonhkg]

WHAT

Add keySetIdentifier to all interfaces & signatures.

Example

const signature = await litClient.chain.raw.pkpSign({
  chain: 'ethereum',
  signingScheme: 'EcdsaK256Sha256',
  pubKey: pkpPublicKey,
  toSign: new Uint8Array([1, 2, 3, 4]),
  authContext,
  keySetIdentifier: 'datil', // or 'naga-keyset1'
});