Implement LoopStateMachine

Utilities for returning state from functions that run inside a loop.

This is used in e.g clipping, where we may need to break or transition states.

The main entry point is to return an [`Action`](@ref) from a function that
is wrapped in a `@controlflow f(...)` macro in a loop.  When a known `Action`
(currently, `Continue`, `Break`, `Return`, or `FullReturn`) is returned, it is processed
by the `@controlflow` macro, which allows the function to break out of the loop
early, continue to the next iteration, or return a value, without being
syntactically inside the loop.

Author: asinghvi17

test/runtests.jl

@@ -11,6 +11,7 @@ end
 
 @safetestset "Types" begin include("types.jl") end
 @safetestset "Primitives" begin include("primitives.jl") end
+@safetestset "LoopStateMachine" begin include("utils/LoopStateMachine.jl") end
 # Methods
 @safetestset "Angles" begin include("methods/angles.jl") end
 @safetestset "Area" begin include("methods/area.jl") end