Dedup reaction triggers

[jhaye]

lf-lang/lingua-franca#1228 contains a test called ReadOutputOfContainedBank for which the last reaction, that has two triggers, fires twice. It should only be called once however, since triggers should be deduplicated.

[oowekyala]

I wonder if #28 might fix this. The problem there was a merge of a reaction into the wrong level. This is the only way AFAIK that a reaction may execute twice at the same time step, since reactions at the same level are already deduplicated.

[jhaye]

I just tried it and it seems like it does!