[PLC] [Test] Added a couple of unsatated builtins application tests

[effectfully]

This adds a couple of tests that builtins can be partially applied.

But we actually had such terms already. For example

-- |  'sum' as a PLC term.
--
-- > /\(s :: *) -> \(ss : size s) ->
-- >     foldList {integer s} {integer s} (addInteger {s}) (resizeInteger {1} {s} ss 1!0)
sum :: TermLike term TyName Name => term ()
sum = runQuote $ do
    s  <- freshTyName () "s"
    ss <- freshName () "ss"
    let sv  = TyVar () s
        int = TyApp () (TyBuiltin () TyInteger) sv
        add = tyInst () (builtin () (BuiltinName () AddInteger)) sv
    return
        . tyAbs () s (Size ())
        . lamAbs () ss (TyApp () (TyBuiltin () TySize) sv)
        . mkIterApp () (mkIterInst () foldList [int, int])
        $ [ add
          , makeDynBuiltinInt sv (var () ss) 0
          ]

I also changed typed generation of terms a bit: it is now more interesting in that it can generate constants in addition to somewhat long terms. I checked manually and observed that indeed more patterns now get generated than previously.

[michaelpj]

Great 👍