[bnporc] Included the "Assurance Vie" domain to BNP iter_accounts

The BNP module did not scrape the "Assurance Vie" space yet, which
may contain additional accounts that are not included in their API.
Among those we can find Life Insurance, Capitalisation contracts and
PERP accounts, and maybe more.
I also implemented the iter_investments() method for this space, however
the domain does not seem to display any kind of transaction history for
these accounts.

Closes: 5016@zendesk