Make curl honor the ~/.netrc file

[tknerr]

This PR adds the -n (i.e. --netrc) flag to all curl invocations across all molior-tools scripts.

With the -n flag present, curl will honor the presence of a ~/.netrc file and will read the login information from there.

• if no ~/.netrc is present, curl will silently ignore that and continue without authentication
• if ~/.netrc is present, but no matching "machine" entry found, curl will silently ignore that and continue without authentication
• if ~/.netrc is present and a matching "machine" entry is found, it will authenticate with the "username" + "password" specified there

This allows you:

• to use molior tools with a molior server / mirror which require authentication (e.g. molior-deploy -m https://my.mirror.org ...
• to use apt sources from a mirror which requires authentication (e.g. molior -p /my/apt/mirror.list ...)

See also:
https://everything.curl.dev/usingcurl/netrc

[tknerr]

I'm not sure if we should add the -n here, because a few lines further down we explicitly pass the $MOLIOR_USERNAME and $MOLIOR_PASSWORD to curl (matching .netrc credentials will likely override these)

[tknerr]

I'm not sure if we should add the -n here, because a few lines further down we explicitly pass the $MOLIOR_USERNAME and $MOLIOR_PASSWORD to curl (matching .netrc credentials will likely override these)