Feature: Remember multiple application windows for "Continue where I left off"

### What feature or improvement do you think would benefit Files?

Currently, "Continue where I left off" will remember tabs on a primary window and reopen them when re-launching Files. However, secondary windows are not remembered, even those opened by the CTRL+N hotkey or respective "New window" command.

This likely is will relate to #14192 at some point, though that feature can likely be implemented separately.

### Requirements

- This proposal will allow Files to open multiple windows on its launch and restore the appropriate tabs to each
- This proposal will initially make most sense within the existing "Continue where I left off", though may make sense as a separate option down the road (or a variation of the option? E.g. some folks may want only one window restored).
- This proposal may require delineating between new windows that are launched as a separate process/instance (compared to any that would be managed by the primary/initial instance).

### Files Version

3.2.2.0

### Windows Version

Windows 11 Pro; 10.0.22621 Build 22621

### Comments

High level, this will likely involve evaluating the process of spawning secondary windows compared to relaunching Files as a separate instance. From there, determining what is affected by this feature's behavior would be easier to understand.

Edit: Builds on discussion at the end of #12624 and #12689 will likely be a prerequisite.

No files, tests, or entry points are named. Start by reviewing how Files spawns secondary windows and how a separate instance is relaunched, then read the discussions in #14192, #12624, and #12689. Done means the Continue where I left off flow restores multiple windows with their appropriate tabs.

Written by the indexing model from the issue text.