LND nodes unable to pay bolt 11 invoice generated with defaults

[endothermicdev]

Issue and Steps to Reproduce

BOLT 11 invoices generated with the default minimum final cltv delta are unable to be paid by LND nodes. This appears to stem from LND using the original default min_final_cltv_expiry_delta of 9 while Core Lightning only generates this field if it's specified as different from the current spec default (18).

lightning-cli decode output:

   "type": "bolt11 invoice",
   "currency": "bc",
   "created_at": 1703009919,
   "expiry": 604800,
   "payee": "redacted",
   "amount_msat": 1000000,
   "description": "testinvoice20231219-4",
   "min_final_cltv_expiry": 18,
   "payment_secret": "2924d1798d1d91cbc7e5c22caea02ced12ab687e42377e9444fb61c8ff19d441",
   "features": "22024100",

LND decodepayreq output:

    "num_satoshis": "1000",
    "timestamp": "1703009919",
    "expiry": "604800",
    "description": "testinvoice20231219-4",
    "description_hash": "",
    "fallback_addr": "",
    "cltv_expiry": "9",

getinfo output

"version": "v23.11",
"blockheight": 821998,
"network": "bitcoin",
"fees_collected_msat": 19642031,
"lightning-dir": "/home/bitcoin/.lightning/bitcoin",
"our_features": {
"init": "08aa802a0a69a2",
"node": "88aa802a0a69a2",
"channel": "",
"invoice": "02000022024100"