system variables which default value changed should use new default value after upgrade

[seiya-annie]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

if use not config these system variable, default value should be new value after upgrade.
foreign_key_checks= old:'OFF' new: 'ON'
tidb_enable_foreign_key= old:'OFF' new: 'ON'
tidb_enable_historical_stats= old:'OFF' new: 'ON'
tidb_enable_plan_replayer_capture= old:'OFF' new: 'ON'
tidb_store_batch_size= old:'0' new: '4'

2. What did you expect to see? (Required)

default value should be same with new scratch cluster

3. What did you see instead (Required)

still use old default value

4. What is your TiDB version? (Required)

v6.6.0-pre