* remove advancedDataSourcePicker feature toggle from DataSourcePickerWithPrompt
* remove advancedDataSourcePicker toggle from DataSourcePicker and adjust tests that relied on old picker
* adjust failing tests in QueryVariableEditorForm
* move DataSourceDropdown to DataSourcePicker file
* covert style declaration syntax to object style in DataSourcePicker
* remove advancedDataSourcePicker feature flag from registry
* remove .only from test
* adjust QueryVariableEditor test to avoid console.error