Always return a number from `table.getn` and `table.getsize`

[Garanas]

The assembly-based functions made by @KionX two years ago were left unused because they were incompatible with the previously existing functions. The Lua implementations would always return a number, regardless of the input type. For non-table types, it would simply return 0.

This is crucial for backwards compatibility. We can't use the faster alternatives until they always return a number.

[KionX]

I don't understand what the problem is.
This function cannot be compatible with getn for performance reasons.
It is imported as getsize2 and empty2. Use them directly for tables.

[Garanas]

I was mistaken - I was referring to table.getsize and table.empty. We can't use the new functions across the code base if they do not have the same behavior. It needs to be backwards compatible.