Fix iter deps

much performance

* don’t enumerate keys, if no deps exist to produce keys
* in v8 for (x in y) where y is non enumerable deopts entire function readmore
* if no deps exists, don't bother iterated the deps... (big win)

TL;DR this reduces the cost of iterDeps by 30%-40% but then also drastically reduces it's usage. In many scenarios it is no longer called at all.