online-accounts: Present all supported providers at once

Instead of having the "more" button which reveals more items to the
providers list.

We still list branded providers above non-branded providers in the
list.

Fixes #1072
7 jobs for online-accounts-show-all-providers in 2 minutes and 1 second (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build #1244401

00:01:27

 
  Test
passed test #1244402

00:00:34

 
  Manual
manual asan #1244404
asan allowed to fail manual
manual flatpak #1244403
allowed to fail manual
manual msan #1244407
allowed to fail manual
manual tsan #1244405
allowed to fail manual
manual ubsan #1244406
allowed to fail manual