Set a default `max_total_routing_fee_msat` of 1% + 50sats

[rust-lightning] / pending_changelog / invoice_request_failed_downgrade.txt

## Backwards Compatibility

* If an `Event::InvoiceRequestFailed` was generated for a BOLT 12 payment (#2371), downgrading will result in the payment silently failing if the event had not been processed yet.