This commit deprecates/replaces the old field `sat_per_byte` with
`sat_per_vbyte`. While the old field suggests sat per byte, it’s
actually using sat per virtual byte. We use the Hidden param to hide all
the deprecated flags. These flags won't show up in help menu onwards,
while stay valid that can be passed from cli. Thus bash scripts
referencing these fields won't be broken.
Previously only the fee rate used for the last sweep (the sweep bucket
average) was reported. This commit adds the request fee preference to
the report, which is used to select a bucket and the sweep tx fee rate.
