feat: support i32, i64, f32, f64 param/return types for Host functions

[mhmd-azeez]

This PR improves implementation of host function calls by removing the limitation of only having I64 params/return types. Now Host Functions can have params/return types of any of the supported types: I32, I64, F32, F64

Example index.d.ts

declare module 'extism:host' {
  interface user {
    floatInputs(p1: F64, p2: F32): I64;
    floatOutput(p1: I32): F64;
  }
}

2. Call Flow

When JavaScript calls a host function:

1. User calls floatInputs (from host.ts)
2. floatInputs calls __invokeHostFunc(index, ...bit_patterns) (from globals.rs)
3. __invokeHostFunc(index, ...bit_patterns) uses __get_function_arg_type (from shim layer) to know the expected type of each parameter, converts them to i64 numbers and then calls __invokeHostFunc (from the shim layer)
4. __invokeHostFunc calls __conv_floatInputs (from shim layer)
5. __conv_floatInputs re-interprets the arguments to the expected types, and does an indirect call to floatInputs (imported from the host)
6. __conv_floatInputs (from shim layer) takes the return value, re-interprets it as i64
7. __invokeHostFunc (from shim layer) returns the return value back to __invokeHostFunc (from globals.rs)
8. __invokeHostFunc (from globals.rs) then uses __get_function_return_type to convert the returned i64 value back to the correct rquickjs type and returns it to floatInputs (from host.ts)

3. Type System

Generated functions include:

// Converters (match import signatures)
__conv_floatInputs(i32, f64, f32) -> i64
__conv_floatOutput(i32, i32) -> i64

// Router (standard 5-param interface)
__invokeHostFunc(i32, i64, i64, i64, i64, i64) -> i64

// Type info
__get_function_return_type(i32) -> i32
__get_function_arg_type(i32, i32) -> i32

4. Generated Host Imports

"extism:host/user" {
  "floatInputs": (f64, f32) -> i64
  "floatOutput": (i32) -> f64
}

[zshipko]

This looks great! It's nice to get rid of all those __invokeHost functions

[bhelx]

A bit tricky to mentally parse but looks correct and the tests look good