[inductor] Make codecache file permissions less restrictive (#100870)
`tempfile.mkstemp` always creates the file `0o600` permissions, so
only the current user can access it. Instead, this salts the original
filename with the pid and thread id to avoid conflicts between
temporary files.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100870
Approved by: https://github.com/jansel
