Don’t replace Stream with LazyList

[julienrf]

Because their behaviour is not the same (LazyList has a lazy head) I think we should not rewrite Stream usage to LazyList. Note that Stream is deprecated in 2.13, though, that’s why I’m not totally sure what should be the right decision.

(this PR depends on #527)

[szeiger]

Can we modularize these rules? It would be nice if you could perform this migration separate from other ones. In most cases you'll want to use LazyList and do not need any additional changes to make it work.

[julienrf]

What we could do:

• provide each rule separately, so that users can have fine grained control on which ones to apply,
• provide a “pack” of rules (ie. a single rule that aggregates several rules) that migrate a 2.12 code base to a 2.13 code base,
• provide a “pack” of rules that migrates a 2.12 code base to a cross-compatible 2.12/2.13 code base (using the collections-compat library).

[julienrf]

I’m closing this PR. We should still provide this rule and let users not apply it if they don’t want to. I’ve created #559 to keep track of that.

[SethTisue]

I hadn't commented because I wasn't sure what I thought about this. But I'm now comfortable with this outcome. 👍