[FIX] base: respect attachment search limit

Configure two companies, add a bunch of attachments to each company so
at least one has more attachments than the default 80 search limit. List
the attachments of that company, only the 7à-ish firsts are displayed
and the pager is disabled.

The `_search` method is override in `ir.attachment` to filter the
original record set. If the original record set had reached the limit,
the filter may only return a subset whose length is lower than the
limit, this trick the different JS views making them think there are no
more records to return and disable the pager.

The fix has been to recursively re-search until the subset length is
equal to the limit.

opw-2025940

closes #34287

closes odoo/odoo#34450

Signed-off-by: Julien Castiaux <Julien00859@users.noreply.github.com>