Change the Implementation of get() in MultiItemCache to Prevent Stack Exhaustion

[dtanders]

One of the projects I'm on at work has such a large number of outputs (currently 1400 and growing) and that is causing webpack to crash during compilation. You can see in the stack trace starting here that the same 6 lines repeat a little over 1200 times until the stack is exhausted. This is because the MultiItemCache in lib/CacheFacade.js uses recursion to iterate over it's item list when you call get(). This implementation prevents stack exhaustion both in the included unit test and in my testing with our project. I'm sure it could be more elegantly written but I've taken care to avoid behavioral changes other than preventing our use case from blowing the stack.

What kind of change does this PR introduce?

This is a bugfix for a probably-rare case in which a large number of outputs causes compilation to exhaust the interpreter stack.

Did you add tests for your changes?

Yes

Does this PR introduce a breaking change?

No

What needs to be documented once your changes are merged?

Nothing that I'm aware of

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[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[sokra]

Thanks

[dtanders]

Thank you