mwexecf() is not effective when sprintf() eats our formatting
prematurely.

…that were missed (#8843)

We want to achieve two things pertaining to /tmp directory
consistency:

1. Avoid using sys_get_temp_dir() which may give the wrong result.
   This includes removing TMPDIR again from lighttpd config.

2. Avoid using /tmp in src/opnsense/mvc to avoid misalignments and
   privilege separation issues.

To do that introduce tempDir into the AppConfig and straighten out
a few related directory handling spots in the same file.

While here delete "app/cache" since it is no longer used.

…8846

…8846)

* CaptivePortal: Implement base_bootgrid_table and base_apply_button

* CaptivePortal: Fix event handler for adding and downloading templates

* CaptivePortal: Fix copy paste error in reconfigure

* CaptivePortal: Expose all fields in search base

* CaptivePortal: Fix Apply button placement