Support large number of SQL-IN parameters in Postgres

Unittest contains good coverage of all cases, however if regression test is needed, one may use any bulk user action to ensure get_in_or_equal works correctly (they all use $DB->get_in_or_equal($SESSION->bulk_users) as part of users processing). For example: a. Make sure you are using Postgresql as db engine. Unit test $ vendor/bin/phpunit lib/dml/tests/pgsql_native_moodle_database_test.php Regression test 1. Create test site, "upload users" from csv, so that you have 65000 users in total. 2. Navigate to Bulk user actions 3. Click "Add all" 4. "With selected users..." set "Delete" and click "Go" - No errors expected. New functionality test 1. Using existing test site, "upload users" from csv, so that you have 65600 users in total. 2. Navigate to Bulk user actions 3. Click "Add all" 4. "With selected users..." set "Delete" and click "Go" - No errors expected.