[FTS-UI] Enrich the editors for collections support

The classic editor currently has this one checkbox that needs to be checked if the user wants their type mappings to accommodate a custom scope and/or collection(s) ..

The checkbox description is a bit distasteful (my doing).

Here's a proposal (http://review.couchbase.org/c/cbft/+/138446) ..

• to move the checkbox out of the "Type Identifier" section as it's applicable to "Type Mappings" as well
• change the description to what the "default" behavior is - i.e stream only `_default._default`; checkbox is therefore checked by default
• add a tooltip describing what un-checking the option would do

Here's the look -