Allow tab title and window title to update independently

Description of the new feature/enhancement

Currently the window title, as seen in the taskbar button, and window
titlebar if "showTabsInTitleBar" is set to false, are always the same as
the tab title for the current tab,

This would allow those two to differ.

The intended use case would be to set a short title for a tab, e.g. "PS" for
PowerShell, while allowing the application title to show as the window
title, where it might contain the current path, e.g. "PS C;\Users\username"

Proposed technical implementation details (optional)

This will require a new setting "suppressApplicationTitleInTab" that
would have a similar effect to the current "suppressApplicationTitle",
but instead of altering both the tab title and window title as the
current setting does, it would only force tabTitle into the tab.

Notes

I've already been working on this, and have a branch in my fork of this repo
that has a working implementation. However, before I create a PR, I'd like to
run the idea past the team, so that they can look it over and give a final
go/no-go decision.

If you want to see it in action, fork my repo: https://github.com/dgnuff/terminal
and take a look at branch features/title, 868e39e .