transaction signing support without agd

[turadg]

What is the Problem Being Solved?

We have interfaces to support clients reading from the chain without spawning a process (@agoric/client-utils) but to sign they need to spawn to agd.

Description of the Design

It could use signAndBroadcast like Keplr's API, which could be implemented by an agd interface too:

makeAgd({execFile}).withOpts({keyringBackend: 'test'}).account('gov1').signAndBroadcast(...)

Requirements if using Casting .

• Given key material, Casting should provide an API to send CosmJS transactions to the leader.

• When you ask Casting to do something, you don't get any state from that call

• New state is propagated through RPC so that all consumers get the same.

• You can evaluate and tell me the results of (with an ACK or a NACK)
  Publishing is how we get the side-effects

Alternately client-utils or rpc.

Should probably make use of,

• re-adopt npm release of cosmology/telescope #10112

Security Considerations

Test Plan

[michaelfig]

Current meet-in-the-middle brainstorm:

test('oracle uses transaction client', async t => {
  const PORT = await t.context.startServer(t, []);
  const leader = makeLeader(`http://localhost:${PORT}/network-config`, {
    retryCallback: null,
    jitter: null,
  });
  /** @type {import('@cosmjs/stargate').SigningStargateClient} */
  const client = leader.makeClient({
    seed: new Uint8Array([0, 1, 2, 3, 3, 2, 1, 0]),
  });
  client.sendAction({
    type: 'applyMethod',
    body: JSON.stringify([
      { '@qclass': 'slot', index: 0 },
      'pushResult',
      [
        {
          numerator: {
            value: { '@qclass': 'bigint', digits: '12345' },
            brand: { '@qclass': 'slot', index: 1 },
          },
          denominator: {
            value: { '@qclass': 'bigint', digits: '67890' },
            brand: { '@qclass': 'slot', index: 2 },
          },
        },
      ],
    ]),
    slots: ['offerResult:3', 'board0133', 'board244'],
  });
});