common: update to latest route-blinding spec.

```
make check-source-bolt CHECK_BOLT_PREFIX="--prefix=BOLT-route-blinding" BOLTVERSION=guilt/offers
```

Other than textual changes, this does:

1. Ensures we put total_amount_msat in onion final hop (reported by @t-bast).
2. Require that they put total_amount_msat in onion final hop.
3. Return `invalid_onion_blinding` exactly as defined by the spec (i.e. less
   aggressive when we're the final hop) (also reported by @t-bast, but I already
   knew).

See: #5823
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-EXPERIMENTAL: `offers` breaking blinded payments change (total_amount_sat required, Eclair compat)

plugins/libplugin-pay.c

@@ -1671,7 +1671,8 @@ static void payment_add_blindedpath(const tal_t *ctx,
 {
 	/* It's a bit of a weird API for us, so we convert it back to
 	 * the struct tlv_tlv_payload */
-	u8 **tlvs = blinded_onion_hops(tmpctx, final_amt, final_cltv, bpath);
+	u8 **tlvs = blinded_onion_hops(tmpctx, final_amt, final_cltv,
+				       final_amt, bpath);
 
 	for (size_t i = 0; i < tal_count(tlvs); i++) {
 		const u8 *cursor = tlvs[i];

plugins/test/run-route-overlong.c

@@ -12,6 +12,7 @@
 u8 **blinded_onion_hops(const tal_t *ctx UNNEEDED,
 			struct amount_msat final_amount UNNEEDED,
 			u32 final_cltv UNNEEDED,
+			struct amount_msat total_amount UNNEEDED,
 			const struct blinded_path *path UNNEEDED)
 { fprintf(stderr, "blinded_onion_hops called!\n"); abort(); }
 /* Generated stub for command_finished */