Load `Main` namespace into infiltrator module

[theogf]

@infiltrate creates a temporary module where local variables and functions are loaded.
However we often need external dependencies in the Main workspace. Of course this can be solved by prepending Main but it's easy to forget/needs more typing.

We could load the Main functions/variables in this local module and make sure that any local variables shadow the Main ones.

[pfitzseb]

I can see that, but I also feel like there's a lot value in @infiltrate behaving like you're actually in whatever scope you put the macrocall, much like an actual debugger would.

[theogf]

Yeah good point, maybe this could be an opt-in feature? (managed by a global flag).