[shader-ast-js] Add mechanism to handle function args with out / inout qualifiers

[postspectacular]

As in JS, GLSL functions can only return a single result, however unlike JS, they can write secondary results into args qualified with out/inout. Due to lack of pointers, there's no easy way to achieve this in JS, unless any such args are wrapped in a temp array which also requires the function call itself to be augmented by the codegen...

Possible approach:

• analyze current scope for function calls with out / inout params
• if present wrap all such vars as array (boxed values)

/**
 * @param x in float
 */
const foo = (x: number) => x + 10;

/**
 * @param x in float
 * @param y in float
 * @param z out float
 */
const bar = (x: number, y: number, z: number[]) => {
    z[0] = x + y;
};

const baz = () => {
    // after pre-analyzing `baz` scope we have determined that
    // y is used as `out` arg by `bar`, so box as array
    let y = [0];
    // call with unboxed value (since no out arg)
    y[0] = foo(y[0]);
    // call with both unboxed and boxed
    bar(1, y[0], y);
    // return unboxed
    return y[0];
};