Standardize os result dataclass documentation

Documentation

• Document times_result and waitid_result with members explicitly. Note the returned module name varies depending on environment (Ex. nt.times_result vs. posix.times_result)
• Between class definition and flag sentences add a sentence referring back to the function that uses the flags (ex. os.wait* + os.WCONTINUED, os.preadv + os.RWF_HIPRI)
• For each dataclass like type ensure there are references to the functions which can produce it.

Spotted by @serhiy-storchaka in https://github.com/python/cpython/pull/151301#pullrequestreview-4492900491

Linked PRs

• gh-157132