Do not cache files in /tmp & remove stm/file_capability dependency

[smortex]

The "intermediate" downloaded files needed to unbreak version change are intended to be preserved between reboots. Drop the caddy::caddy_tmp_dir parameter and store cached downloads in /var/cache instead of the temporary directory.

Also include:

• 90

• 93

• 95

[bastelfreak]

thanks for the work! Added the backwards-incompatible label because this removes a parameter.