Emit LIMIT -1 when offset is used without limit (#821)

* Emit LIMIT -1 when offset is used without limit, closes #816

SQLite requires a LIMIT clause to appear before OFFSET, so passing offset
without limit generated invalid SQL such as:

    select * from "t" offset 2

which raised OperationalError: near "2": syntax error.

A negative limit means "no upper bound" in SQLite, so "limit -1 offset N"
returns all rows from position N onwards.

Fixed in three places that build LIMIT/OFFSET SQL:

- Queryable.rows_where() - also covers pks_and_rows_where()
- Table.search_sql() - also covers search()
- the "sqlite-utils rows" CLI command

* Remove duplicate comments

---------

Co-authored-by: ethanhawkes-gif <259455325+ethanhawkes-gif@users.noreply.github.com>

tests/test_rows.py

@@ -59,6 +59,9 @@ def test_rows_where_order_by(where, order_by, expected_ids, fresh_db):
         (None, 3, [1, 2, 3]),
         (0, 3, [1, 2, 3]),
         (3, 3, [4, 5, 6]),
+        # offset without limit should return every remaining row
+        (97, None, [98, 99, 100]),
+        (0, None, list(range(1, 101))),
     ],
 )
 def test_rows_where_offset_limit(fresh_db, offset, limit, expected):
@@ -70,6 +73,12 @@ def test_rows_where_offset_limit(fresh_db, offset, limit, expected):
     ]
 
 
+def test_pks_and_rows_where_offset_without_limit(fresh_db):
+    table = fresh_db["rows"]
+    table.insert_all([{"id": id} for id in range(1, 6)], pk="id")
+    assert [pk for pk, _ in table.pks_and_rows_where(offset=3, order_by="id")] == [4, 5]
+
+
 def test_pks_and_rows_where_rowid(fresh_db):
     table = fresh_db["rowid_table"]
     table.insert_all({"number": i + 10} for i in range(3))