fix(core/select): editable select not opening

[matthiashader]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (yarn build) was run locally and any changes were pushed
• Unit tests (yarn test) were run locally and passed
• Visual Regression Tests (yarn visual-regression) were run locally and passed
• Linting (npm lint) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• Bug fix
• Feature
• Refactoring (no functional changes, no API changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

• the dropdown is not opening
  -> open the dropdown by the button on the right side

• the list is not filtered

• if the dropdown is open before editing the text, the list got filtered as expected

• the focus does not work on tab --> Dropdown not showing up
  GitHub Issue Number: Editable select is not opening when selecting it #832 , [ix-select] When tabbing into an ix-select, the dropdown options don't show up #773

What is the new behavior?

• dropdown-list opens when clicking on the ix-select (e.g. enabled by a property)

• filtering works if the list is opened with the button

• Dropdown opens when using tab

Does this introduce a breaking change?

• Yes
• No

Testing

Other information

[nuke-ellington]

Fixed in #784