Add more functions for ensuring nodes via MastForestBuilder

[sergerad]

Closes #1355

Add methods toMastForestBuilder to facilitate ensuring nodes with fewer LOC

[sergerad]

Hey @plafer reviewers aren't assigned automatically and I can't request reviews. This one is ready for review.

[bobbinth]

Looks good! Thank you for tackling this one as well!

Overall, I think the solution works but we probably want to add convenience methods for other nodes too (e.g., for Join, and Split nodes). For these, I don't think we can use the Into approach (or at least I'm not sure how). So, we may end up needed MastForestBuilder::ensure_join(), MastForestBuilder::ensure_split() etc.

If we do the above, we might want to have a similar approach for basic blocks. Though, I agree, MastForestBuilder::ensure_basic_block() does not look as elegant as the current solution. Maybe, we can just say MastForestBuilder::ensure_block().

Separately, and not for this PR, I find the fact that we need to say "basic_block" in various places pretty cumbersome. Maybe we should just say "block" everywhere instead. @plafer and @bitwalker, curious what you think on this.

[bobbinth]

Here is an example where instead of:

let nested = {
    let node = MastNode::new_split(r#true2, r#false2, expected_mast_forest_builder.forest());
    expected_mast_forest_builder.ensure_node(node)
};

We should be able to do something like:

let nested = expected_mast_forest_builder.ensure_split(r#true2, r#false2);

[sergerad]

@bobbinth I have made the suggested changes.

LMK if you prefer having separate functions as opposed to the Option<DecoratorList> for ensure_block().

[bobbinth]

Looks good! Thank you! I left one small comment inline. After it is addressed, we can merge.

LMK if you prefer having separate functions as opposed to the Option<DecoratorList> for ensure_block().

I think the way you have it now looks good - so, no need to change anything in this regard.

[sergerad]

Just wondering whether we want to do the same for MastForest::add_node() which is used similarly. E.G:

let dyn_node_id = {
        let node = MastNode::new_dyn();
        mast_forest.add_node(node).unwrap()
    }

[bobbinth]

All looks good! Thank you!

Just wondering whether we want to do the same for MastForest::add_node()

Yes - that would be great! But I'd do it in a separate PR.