Add dynamic function input-output.

[AdvancedAntiSkid]

Is your feature request related to a problem? Please describe.
Many users of HTSL have started using special stats as function inputs and outputs. HSL should support this by converting parameters to special stats, that the function call can prepare and the function itself consume.

Describe the solution you'd like
Treat function parameters as special stats. Implement function invocation with parameters. Functions should also be able to return values, and those should also be special stats. You may want to allow tuple-like returns.

Describe alternatives you've considered
Hypixel runtime does not really allow anything else.

Additional context
Use return values with caution, as Hypixel function triggers do not guarantee to wait until function completes, so the return stat may not be correct.

[AdvancedAntiSkid]

To make function return values stable, we might need to wrap the code following a function call into a merge function, that is triggered by the function that was initially called. However this would only work for internal functions defined in the HSL source code.