Allow change the use of Global Search by Classic Search Window when performing a search from the widget.

[IagoSRL]

A user asked about implement search from the Unified Search Widget using the Classic Search Window that has some advantages as it does truncated search by default without use wildcards (new Global Search search ever complete words, except if '*' wildcard is used).

Its not clear if is possible with the Thunderbird API request the opening of that window with search keywords and auto search, some investigation required.

If is possible, can be a preference under extension options for user that want the classic search.