Refactor temporary directory handling

[harp-intel]

• --tempdir flag overrides default (usually /tmp) in case /tmp is on a filesystem mounted with the 'noexec' option
• improve error messages, e.g., when temp dir lands on a 'noexec' file system
• eliminate --targettemp flag

There are two temporary directories created.

• for the application, this is where dependencies and scripts are written before being copied to the target
• for the target (remote or local), this is where the scripts and dependencies are stored and executed (must not be 'noexec')

Only the 2nd temporary directory location can be changed with --tempdir. The 1st always lands in the system's default temp, e.g., /tmp.

Both directories are cleaned up (removed) when the application exits...unless the --debug flag is specified.