show current timestamp in the Date Time picker field

Summary:

With the implementation of JRACLOUD-71348, users can now either provide the value for the 'date time picker' field manually or select a given time. 

Enhancement request:

Please provide the functionality to work as follows:

• If the custom field is empty and the user clicks on it, then the system should show the current date and time automatically as a preset value

Use case:

Consider the example of end-users from a telephone switchboard domain, they need to export the reports having exact date and time and currently, they have to manually fill the value in the field.