Show terminals separately in quickOpenTerm and quickOpenView

[gioragutt]

Fixes both quickOpenTerm and quickOpenView command.

[msftclas]

All CLA requirements met.

[gioragutt]

@Tyriar The code pretty much ends up changing from iterating over tabs or instances, to iterating over the instances in tabs.

This seems like a bit of code rep, but I can't think of a way of removing it, other than exporting some method from TerminalService which returns:

interface TerminalInTab { // or w/e
  tabIndex: number;
  terminalIndex: number;
  terminal: Terminal;
}

and thus we can make the usages outside terminal service be able to just forEach or map/reduce once, instead of doing the nested loops due to having to iterate over terminals in tabs.

[gioragutt]

@Tyriar any comments?

[Tyriar]

Works great, thanks! 😃

[gioragutt]

@Tyriar thanks man! Glad to contribute!