Various functions missing self parameter

[timohanke]

One example: Nat16.bitcountLeadingZero

There are many related functions in the same module and in other modules (Nat32, Nat64, ...). Too many to name here.

[crusso]

I think we decided to (for now) only selfify functions on data structures, not scalars, though I agree the distinction is a bit vague.

[timohanke]

Except some functions like toNat, toNatX, toText which are available even for scalars.

[crusso]

True.