Scale incomplete funding period down

[gordsport]

In order to complete the perps funding work we need to implement the specced changes relating to scaling incomplete funding periods down by the fraction of the funding period spent outside of auction mode.

Details can be seen in the specs PR:

• More funding payments during auctions and suspended markets specs#2098

[gordsport]

Closing as a dupe of:

• Scale funding payment by fraction of period spent outside of auction #10360