Split up core/test/iter.rs into multiple files This PR removes the `// ignore-tidy-filelength` at the top of [iter.rs](04f44fb923/library/core/tests/iter.rs
) by splitting it into several sub files. I have split the file per test, based on what I felt the test was really trying to test. Addresses issue #60302. - [associated_util.rs](d29180a8ed/library/core/tests/iter/associated_util.rs
) - For testing the module level functions. (Maybe should be renamed?) - [collection.rs](d29180a8ed/library/core/tests/iter/collection.rs
) - For testing methods that use the values of all the items in an iterator, and creates one value from them, whether it be a Vec of all the values, or a number that represents the sum. - [mod.rs](d29180a8ed/library/core/tests/iter/mod.rs
) - For utility structs used in all tests, and other tests I didn't know where to place. - [range.rs](d29180a8ed/library/core/tests/iter/range.rs
) - For testing ranges. - [transformation.rs](d29180a8ed/library/core/tests/iter/transformation.rs
) - For testing methods that transform all the values in an iterator. - [util.rs](d29180a8ed/library/core/tests/iter/util.rs
) - For testing methods that provide utility in more specific use cases. "Programatically" ----------------------- You may have noticed I "Programatically" split up the file. [This is how](https://gist.github.com/danii/a58b3bcafa9faf1c3e4b01ad7495baf4) I managed to do that. 😛 Hope that's fine.