Background
This bug is similar to the bug fixed in T398428.

If a user is typing in one of the inputs created by NamespacesControl, such as "Namespaces with the help panel disabled in both reading and editing mode," and then clicks outside of the dropdown menu, their typed input automatically converts into a chip. Ideally, typed input only becomes a chip after the user selects an item from the dropdown menu. In this scenario, the typed input should remain input. Additionally, after users select an item from the dropdown menu, the input should clear.

Users should only be able to select name spaces from the dropdown menu. Users should not be able to enter custom input.

Lastly, this task requires adding MultiselectLookup to the NamespacesControl.

Acceptance Criteria

• Replace CdxChipInput and CdxMenu with MultiselectLookup.
• Ensure input clears after a user selects an item from the dropdown menu.
• Ensure users can select menu items from the dropdown menu.
• Ensure that if a user enters input which is already a chip, they can deselect that item from the dropdown menu.
• If a user clicks outside of the dropdown after typing input, the typed input should remain input.

Antigoals
This task does not require highlighting the search query in menu items.