* If target:esnext,then useDefineForClassFields: true will now be the default.
* Added error if a private identifier is used in a static a initializer if target:ESNext and useDefineForClassFields:false.
* Added test for new useDefineForClassFields default and error message.
* Fixed tests after changing the default of useDefineForClassFields to true for target esnext
* Fixed code review suggestions.
* Updated error message.
* Added missing static check for the containing property. Fixed other code review issues.