Add `emit` assembly instruction about miden-vm

[frisitano]

This sounds good. One potential extension to this could be to also allow for parameters to be passed via the decorator, e.g. emit.<event_id>.<param_1>.(...).<param_n>, this would then be parsed into a struct of the form:

pub struct Event {
    id: u32,
    params: Vec<u32>
}

However, I can't think of any immediate use cases in which parameters would be required so maybe we go with the simple case as described in the opening post. To better support this intuition, I will asses our requirements of how events will be used in miden-base and create an issue to detail this.

[frisitano]

closed by: #1119