PS-9293, PS-9328: Fix innodb.parallel_read_kill test failures.

After Upstream's fix for bug#35952353 "SELECT COUNT(*) degraded performance on
8.0 compared to 5.7" (mysql/mysql-server@ffad6cf)
MySQL stopped using parallel read for COUNT(*) evaluation when secondary index
scan is used.

As result innodb.parallel_read_kill test started to fail, as it employed
COUNT(*) that used secondary index scan to test InnoDB parallel read
killability. The parallel read code is simply no longer invoked causing
DEBUG_SYNC time out.

This patch fixes the failure by forcing the test to use COUNT(*) that
uses primary key scan, which is still processed using parallel read,
instead.

Author: dlenev

mysql-test/suite/innodb/r/parallel_read_kill.result

@@ -12,8 +12,8 @@ END|
 CREATE TABLE t1(
 f1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
 f2 INT NOT NULL,
-f3 INT NOT NULL,
-KEY(f2, f3))
+f3 INT NOT NULL
+)
 ENGINE=INNODB;
 BEGIN;
 # Create uncommitted rows

mysql-test/suite/innodb/t/parallel_read_kill.test

@@ -19,8 +19,8 @@ DELIMITER ;|
 CREATE TABLE t1(
     f1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
     f2 INT NOT NULL,
-    f3 INT NOT NULL,
-		KEY(f2, f3))
+    f3 INT NOT NULL
+    )
 ENGINE=INNODB;
 
 BEGIN;