decode: don't fail to decode just because a bolt12 invoice has expired.

[rustyrussell]

In fact, there are several places where we try to decode old invoices, and they should all work. The only place we should enforce expiration is when we're going to pay.

This also revealed that xpay wasn't checking bolt11 expiries!

Reported-by: hMsats
Fixes: #7869

Changelog-Fixed: JSON-RPC: decode refused to decode expired bolt12 invoices.

[vincenzopalazzo]

ACK 6ccc2dc

[hMsats]

Copied all the changes and decode now decodes an expired bolt12 invoice correctly.

For xpay

Now:

lightning-cli xpay lnbc3u1pn5kqycsp5qu4fgcfkxjfg55d9aqs2mv34guk7cfwm6eeg624v8hvxsmxzw9espp5twhxl6us5mvsr5a0rl6fzaaa2v3zshufdz8shdc3ry0v5tax4ygqdquw3jhxazlv4u8qunfwfu477rsv9usxqppcqpjrzjqtc63jrkql6ptj8j9sq9jvqzwav5rh4y3p5uugcfdte8kr8aes9kjrrqnqqq90qqqqqqqqqqqqqqraqqjq9qxpqysgq9q2pjhfcka3ad27vqjpqvw88779km7sh2dzsxney90mcf4yu90wkvqf2mw5y8t4al6nhqld97su6smf3e40mrt98rd86kmhy8zy78tqp9fecjp
{
   "code": 207,
   "message": "Invoice expired 216 seconds ago"
}

Before:

lightning-cli xpay lnbc3u1pn5kqycsp5qu4fgcfkxjfg55d9aqs2mv34guk7cfwm6eeg624v8hvxsmxzw9espp5twhxl6us5mvsr5a0rl6fzaaa2v3zshufdz8shdc3ry0v5tax4ygqdquw3jhxazlv4u8qunfwfu477rsv9usxqppcqpjrzjqtc63jrkql6ptj8j9sq9jvqzwav5rh4y3p5uugcfdte8kr8aes9kjrrqnqqq90qqqqqqqqqqqqqqraqqjq9qxpqysgq9q2pjhfcka3ad27vqjpqvw88779km7sh2dzsxney90mcf4yu90wkvqf2mw5y8t4al6nhqld97su6smf3e40mrt98rd86kmhy8zy78tqp9fecjp
{
   "code": 203,
   "message": "Destination said it doesn't know invoice: incorrect_or_unknown_payment_details"
}