test_classes: Improve assert_database_query_count output message.
test_classes: Improve assert_database_query_count output message.

Output message should talk about both the cases:
actual_count > expected_count and actual_count < expected_count.

The message now includes information for the case where
actual_query_count < expected_query_count.

Fixes: #23325

zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip