test(iroh-cli): Also test for "minutes" in transfer time regex 😬 (#2475)

## Description

Windows CI was so slow, the transfer was measured in *minutes*, not
*seconds* and printed as such to the CLI.

The CLI tests only expected "seconds" to be printed though. 😬 

Also went ahead and improved performance of `make_test_file` because
damn this test is already slow enough.

## Breaking Changes

None

## Notes & open questions

Idk, do you have any? :P

## Change checklist

- [X] Self-review.
- ~~[ ] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.~~
- ~~[ ] Tests if relevant.~~
- ~~[ ] All breaking changes documented.~~