This commit changes the behavior of the expand/collapse
translations button in the new design. Now, unless a
particular language is selected in "Show translations in":

- if the user has two profile languages or more, then hide
  non-profile-language translations behind the
  expand/collapse button.

- if the user is logged out or has one profile language or
  less, then keep the existing behavior of only showing the
  first five translations.

This will hopefully show more relevant results by default.

So that it’s gonna be easier to add custom entries.

This commit changes the behavior of the expand/collapse
translations button in the old design. Now, unless a
particular language is selected in "Show translations in":

- if the user has two profile languages or more, then hide
  non-profile-language translations behind the
  expand/collapse button.

- if the user is logged out or has one profile language or
  less, then keep the existing behavior of only showing the
  first five translations.

This will hopefully show more relevant results by default.

This variable counts sentences that are initially
hidden, so it should be named "hidden" or
"toDisplay" or similar.

Now that this button can hide *all* the
translations, it would not make sense to make it
say "show n more translations" in that case.

Also included the icon inside the translatable
string to allow translators to put it at a
different place (this should be useful for RTL
languages).

Apply the same changes as in
46c8d6b
on the new design.