expose promise rejection tracker

[Gentle]

this enables users to write a custom onerror handler for uncaught rejected promises

the parameters are currently the same as the C API has, this function receives both handled and unhandled rejections.

For the purpose of onerror, you would ignore all calls where is_handled is true as below

example usage:

use rquickjs::{Context, Runtime};

fn main() {
    let runtime = Runtime::new().unwrap();
    let context = Context::full(&runtime).unwrap();
    runtime.set_host_promise_rejection_tracker(Some(Box::new(
        |_ctx, _promise, reason, is_handled| {
            if !is_handled {
                dbg!(reason);
            }
        },
    )));
    context
        .with(|ctx| {
            let _: () = ctx
                .eval("function x() { new Promise(() => { throw new Error('42') }) }; x()")
                .unwrap();
        });
}

[Gentle]

where would I put a test for this?

[Gentle]

ok, while this works, it causes ref_count errors, I got these logs when debugging

Assertion failed: p->ref_count == 0 (/Users/gentle/work/quantum/quantum-native/target/wasm32-wasip1/wasm-release/build/rquickjs-sys-c03be711d9001ed4/out/quickjs.c
free_zero_refcount: 5617)

I'll try debugging further tomorrow, do you have any insights on what needs to be changed?

[Gentle]

I think the refcount error happens because I capture Ctx in a closure here but I'm still trying to figure out how to do that differently

[Gentle]

the current iteration is sometimes causing the garbage collector to crash when shutting down, but otherwise does the job

[Gentle]

I'm happy to say I fixed it, I'll write a test tomorrow

[DelSkayn]

Looks good, just need a change to the test to make sure it runs when parallel is enabled.

[DelSkayn]

LGTM