[BUGFIX] Handle large number of pages in linkvalidator

This patch handles problems which occured with a large number of pages
and also for a large number of records to be checked for broken links.
The problems previously resulted in "Prepared statement contains too
many placeholders" exceptions and consumption of too much RAM and
(possibly) out of memory errors.

Technical details about the implementation follows because this is
handled slightly differently than in other areas of the core.

LinkValidator used named placeholders to build database queries,
and the EditableRestriction class also used a number of placeholder.

Technically 'doctrine/dbal' explodes named placeholders for array
values with quote type 'PARAM_INT_ARRAY' or 'PARAM_STR_ARRAY' to
single unnamed placeholders for each value, using one placeholder
for each array value. If multiple array value placeholder are used
with a large number of values this could quickly emit the "Prepared
statement contains too many placeholders" error as the li...