File Manager: "Open terminal here" feature does not clean up temporary files

[mgutt]

This feature was introduced with PR #2501:

It creates temporary shell scripts, which are not cleaned up:

root@atum:/mnt/disk1/test# ls /var/tmp/File_Manager_17681682*
/var/tmp/File_Manager_1768168229540.run.sh*  /var/tmp/File_Manager_1768168250743.run.sh*

In addition it does not really make sense to create timestamp based filenames. We should use the usual file manager name scheme and for example:

/var/tmp/file.manager.terminal.sh