[Feature request] Add compilers hint like c++ [[likely]] and [[unlikely]]

[gitfede56]

Just a thought, not a priority, but since mojo is also about performance I would personally like to have compiler hints like c++ [[likely]] and [[unlikely]] to set the default branch prediction at runtime (at comptime there is already the amazing @parameter)

Syntax example:

fn factorial(n: Int) -> Int
    @predict(True) # or '@likely'
    if (n > 1):
        return n * factorial(n - 1)
    else
        return 1

fn maybe_get_something(item: Item) -> Optional[Int]
    @predict(False) # or '@unlikely'
    if not item.is_valid():
        return None

    # do something with item
    return item.get_some_int()