This diff introduces the possibility of specifying --input-file file
multiple times to force ooniprobe to read inputs from file.
Like we do for miniooni, the file shall contain a single entry per
line and this entry should be a URL for websites.
Likewise, one can specify --input URL multiple times.
This implementation is a very simple, initial implementation and there
is a bunch of changes I'd like to add on top of it.
And also perhaps a bunch of cleanups.
I've chosen to expose these flag _only_ for websites for now.
Part of https://github.com/ooni/probe/issues/1283.
cfd3b8f9b2