add suffix kwarg to `tempname` (#53474)
`tempname` checks that the name its returning is not already a file,
however if you want that filename to contain other information, like a
file extension, that can mean the uniquing isn't complete.
This adds `tempname(suffix = "_foo.txt")` to include a suffix in the
name and uniquing check.
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Co-authored-by: Jameson Nash <vtjnash@gmail.com>
