[WIP] remove tempname usage


|Q            |A  |
|---          |---|
|Bug Fix?     |n  |
|New Feature? |n  |
|BC Breaks?   |n  |
|Deprecations?|n  |
|Tests Pass?  |n  |
|Fixed Tickets| #9238 |
|License      |MIT|
|Doc PR       |   |

from the list:

- [x] escapeshellarg() and escapeshellcmd()  (?)
- [x] exec() (used by the Console, so not relevant)
- [x] highlight_file() (only used for debugging purpose, so not relevant)
- [x] proc_close(), proc_open() and proc_terminate() (used by the Process component, no way around it)
- [x] shell_exec() (used by the Console, so not relevant)
- [x] symlink() (used by the Filesystem and Finder) - used only in assets:install which is useless to do in GAE ready only FS
- [x] tempnam() - addressed in this PR