gh-120057: Add os.reload_environ() function (#126268)

Replace the os.environ.refresh() method with a new
os.reload_environ() function.

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>