Implement basic function inlining

[GearsDatapacks]

As discussed in #3722, and this thread.
As pointed out here, some key functions such as bool.guard can cause a stack overflow with recursion in javascript, while giving a false appearance of being tail recursive.

Inlining bool.guard would solve this issue. As Louis suggested, we could initially implement a basic version of inlining (i.e. the inlining itself, without complex heuristics etc.), and later we can expand and improved upon this. @lpil could you elaborate a bit on how you were imagining we would decide which functions to inline?

I did a bit of research into how function inlining works when the about discussion was first created, so I'll write up a quick summary of how this will work soon, and then I'll look into implementing this.

[lpil]

Thank you