`test_itertools.py` does not test infinite iterable for `itertools.chain.from_iterable`

[youknowone]

Bug report

itertools.chain.from_iterable is safe to use with infinite iterable, but no test exists.

example:

chain.from_iterable(repeat(range(5)))

Your environment

• CPython versions tested on:
  3.10.4 and current main branch

• Operating system and architecture:
  N/A

[rhettinger]

ISTM there is no point in adding another test for this. Infinite iterators a just a special case of "bigger than you can reasonably consume".

From a consumers point of view, there is no way to differentiate an infinite iterator from a huge iterator (c.f. the halting problem).

[youknowone]

The test will prevent a potential regression to evaluate given iterable before consuming.

Please let me know if there is a test already covers a huge iterator.
I found test_long_chain_of_empty_iterables is a similar one, but it doesn't fully prevent it.

ref: RustPython/RustPython#3787