sql: optimization for full-key 'DELETE WHERE'

Currently, OP_Delete (i.e. VDBE opcode which implements delete logic) can operate only on cursors: firstly it is required to open cursor, then to position this cursor to record to be deleted (by fetching tuple into cursor), to handle all checks in 'WHERE' clause and finally fetch key from tuple and delete record. However, if all key fields are specified in 'WHERE' clause and there are no other conditions, we are capable of deleting record without cursor positioning.
For instance:

\set language sql
CREATE TABLE t1(id PRIMARY KEY, a, b, c);
INSERT INTO t1 VALUES (1, 2, 3, 4), (2, 0, 2, 3), (3, 1, 0, 3);
DELETE FROM t1 WHERE id = 1 or id = 3; 

Start by tracing the OP_Delete VDBE opcode and the SQL DELETE path described in the issue. Use the provided CREATE TABLE, INSERT, and full-key DELETE example to compare behavior, and consider the work complete when qualifying deletes can avoid cursor positioning without changing the resulting rows.