Add integration test for MuSig2RegisterCombinedNonce and
MuSig2GetCombinedNonce RPCs to verify the coordinator pattern workflow.
The test:
- Creates three signing sessions without initial nonce exchange
- Manually aggregates nonces using the coordinator pattern (btcec musig2)
- Tests v0.4.0 returns unsupported errors (as expected)
- Tests v1.0.0rc2 successfully registers and retrieves combined nonces
- Verifies mutual exclusivity (error: already have all nonces)
- Completes a full signing flow to ensure signatures are valid
Also adds the required RPC harness wrapper methods to lntest/rpc/signer.go for
the new RPCs and adds MuSig2RegisterNoncesErr wrapper for error testing.
This demonstrates that the "imported" account behaves differently for a
wallet that's watch-only vs. normal. The testTaprootImportTapscriptFullKeyFundPsbt
test case succeeds in a normal run but fails in a remote-signing setup.
For some reason, an imported tapscript address ends up in the "default"
account when remote-signing but in the "imported" account for a normal
wallet.
This commit removes the usage of the standby nodes and uses
`CreateSimpleNetwork` when applicable. Also introduces a helper method
`NewNodeWithCoins` to quickly start a node with funds.
Prepares the upcoming refactor. We now never call `ht.Alice` directly,
instead, we always init `alice := ht.Alice` so it's easier to see how
they are removed in a following commit.
Elle Mouton