A previous change fixed compatibility with Scratch 2 removing 3's
unintentional scope leaking. This furthers that change so that
procedures with no parameters will also not accidentally use values in
other procedure stacks.
Use getProcedureParamNamesIdsAndDefaults to get the defaults along with
names and ids so defaults may be set for a procedure call if the
parameter is not provided.
Use a private StackFrame class to help internally manage use of Stack
Frame values and memory. Create params, reported, and executionContext
on demand.
blockUtility as an object literal inside execute creates 11 objects,
one for the object, and 10 for the function closures. As a separate
object and allocated once, setting its sequencer and thread members,
block functions can share the same util object. Extract blockUtility to
cut down on allocations.
