Upgrade select2 to stable version 4.0.4 and fix compatibility issues in Civi

Currently, Civi is using select2 3.5 which we need to upgrade to latest stable 4.0.4 (https://github.com/select2/select2/releases) and also resolve compatibility issues with CiviCRM.

Major issues:

1. Auto appending values doesn't work anymore Error: Uncaught TypeError: Cannot read property 'prop' of undefined LOC - https://github.com/civicrm/civicrm-core/blob/master/js/crm.searchForm.js#L9 Reference - https://select2.org/upgrading/migrating-from-35#select2-val

2. Placeholder broken Error: Uncaught TypeError: Cannot read property 'id' of undefined As per 3.5 - placeholderOption is used to set the placeholder value for select2 widget As per 4.0.4 - placeholder option can now accept placeholder value both in string and object Reference - https://select2.org/upgrading/migrating-from-35#more-flexible-placeholders

3. EntityRef select2 fields are broken Error: Uncaught Error: No select2/compat/initSelection As per 4.0.4 - Removed the requirement of 'initSelection' Reference - https://select2.org/upgrading/migrating-from-35#removed-the-requirement-of-initselection

4. Navigation menu style is not applied Error: Uncaught TypeError: Cannot read property 'prop' of undefined As per 4.0.4 - $("select").val("1").trigger("change"); // instead of $("select").select2("val", "1"); Reference - https://select2.org/upgrading/migrating-from-35#select2-val

5. Broken entityRef field There are multiple issues with an entityRef field which are listed below:

6. Placeholder doesn't show

7. Unable to populate data via REST API link

8. Create contact dialog box doesn't render below the search field

9. Escape text doesn't show up

10. Action-menu select2 doesn't work on selecting record(s) in a search list It throws an error Uncaught TypeError: Cannot read property 'apply' of undefined after Search and also action-menu field doesn't behave on selecting a record.

11. The native crm CSS styling doesn't apply on select2/4.0+ widget

Minor issues

1. Multi select2 widget doesn't show downarrow placeholder icon
2. select2 css style aren't applied after upgrade