lwk: increase default context timeout

[YusukeShimizu]

increase default context timeout from 5 seconds to 20 seconds.

[grubles]

Running lbtc-getbalance took 7.2 seconds this time, which would've produced an error previously but with the new timeout was given enough time to complete.

$ time ./builds/peerswap/out/pscli lbtc-getbalance
{
  "sat_amount": "93373298"
}

real    0m7.204s
user    0m0.011s
sys     0m0.010s

LWK-enabled peerswapd as swap sender takes 33.5 seconds to initiate a swap and is able to succeed instead of failing:

$ time ./builds/peerswap/out/pscli swapin --channel_id 214039729557274624 --sat_amt 10000001 --asset lbtc
{
  "swap": {
    "id": "d4632b9394cbe1375d411cd383c32bf5d3c2deba017d7e830edb025824702ea5",
    "created_at": "1731598740",
    "asset": "lbtc",
    "type": "swap-in",
    "role": "sender",
    "state": "State_SwapInSender_SendTxBroadcastedMessage",
    "initiator_node_id": "035ca2fe4793a5e789ce846062eb4834f573c060d9200ce77544a29b48a0aa5923",
    "peer_node_id": "036e680823a129ac9a2eeb8c43514a5b6cb09ae28e3e698a0e34aaa8865d6cc344",
    "amount": "10000001",
    "channel_id": "194668:21:0",
    "opening_tx_id": "64ef9e855a7d0236deb3fbf34864349f0689886a47a61f011379a22b969e27df",
    "claim_tx_id": "",
    "cancel_message": "",
    "lnd_chan_id": "214039729557274624"
  }
}

real    0m33.553s
user    0m0.011s
sys     0m0.009s

Tested ACK 79274df