Should avoid use 'testing.refreshTests'

[jdneo]

testing.refreshTests has been removed in VS Code so we need to use the extension customized one

[jdneo]

To verify this issue (only used for tester):

1. Open an invisible project containing unit test
2. Change the source path in classpath configuration page
3. Check if the test explorer will refresh automatically after source page is changed

[Eskibear]

verified.