benchmark: make temp file path configurable

In three fs benchmarks, a temp file is created in the source tree. For
tests, allow the location to be configurable so it gets written to the
test temp directory instead.

Additionally, shave about a second off the test running time by setting
`dur` to `0.1` instead of `1`.

PR-URL: https://github.com/nodejs/node/pull/17811


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>