[IMP] *: limit in search panel

This commit introduces a new attribute 'limit' for search panel fields
that allows to avoid performance issues. That integer attribute (with
default 200) allows to fix a maximal number of values to display for the
fields. When the number of field values to display reaches the limit,
no values will be displayed. Instead, a warning message will be shown
in the corresponding search panel section.
Note it is possible to have no limit using limit="0" on a field.
This commit reintroduces in a better way the principle brought by the
fix 8d57153b.

Task ID: 2154749