Windows: Moved "kill on close" job object flag to own function.
Windows: Moved "kill on close" job object flag to own function.

Instead of setting this flag unconditionally when we create a job
object, this patch abstracts it to the function
`set_job_kill_on_close_limit(pid_t)` so that users can choose how to tie
job object lifetimes together.

Review: https://reviews.apache.org/r/65399

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