Change JS_IsArray to not transparently detect proxies

[bnoordhuis]

JS_IsArray currently has this prototype:

/* return -1 if exception (proxy case) or true/false */ 
int JS_IsArray(JSContext *ctx, JSValue val)

That's jarringly different from JS_IsObject/JS_IsPromise/etc. and returning a ternary instead of a boolean like the other functions is a bug magnet.

The reason it takes a JSContext pointer as its first argument is because it transparently handles proxies and guards against stack overflow in case the proxy's target object loops back on itself.

I don't think it should try to handle proxies because that's inconsistent. Neither JS_IsObject or JS_IsPromise do that, for example.

My proposal:

1. definitely remove proxy handling from JS_IsArray

2. optionally add a JS_IsProxy function and maybe JS_GetProxyTarget + JS_GetProxyHandler?