Spend reinstated utxos when disconnecting a failed withdrawal bundle

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disconnect_withdrawal_bundle_failed has an inverted check on the utxo delete:

if state.utxos.delete(rwtxn, &OutPointKey::from(outpoint))? {
    return Err(error::NoUtxo { outpoint: *outpoint }.into());
};

delete returns true when it actually removes an entry. When a known withdrawal bundle fails, connect_withdrawal_bundle_failed reinstates its utxos as spendable. So on disconnect the utxo is present, delete returns true and the function errors with NoUtxo in the normal case.

The result is that a reorg disconnecting a block that carries a Failed event for a known bundle always fails, leaving the node unable to follow the better mainchain branch. Every other delete check in the file is correct.

Fix

Negate the condition so it errors only when the utxo is unexpectedly absent and spends it back into stxos otherwise.

Test

Added a unit test that reproduces the post-failure state (known bundle with its utxo reinstated), disconnects the failure and asserts the utxo is re-spent. It fails on the old code with the NoUtxo error and passes with the fix.