## Summary of the Pull Request
Enables the `toggleFullscreen` action to be able to enter fullscreen mode, bound by default to <kbd>alt+enter</kbd>.
The action is bubbled up to the WindowsTerminal (Win32) layer, where the window resizes itself to take the entire size of the monitor.
This largely reuses code from conhost. Conhost already had a fullscreen mode, so I figured I might as well re-use that.
## References
Unfortunately there are still very thin borders around the window when the NonClientIslandWindow is fullscreened. I think I know where the problem is. However, that area of code is about to get a massive overhaul with #3064, so I didn't want to necessarily make it worse right now.
A follow up should be filed to add support for "Always show / reveal / never show tabs in fullscreen mode". Currently, the only mode is "never show tabs".
Additionally, some of this code (particularily re:drawing the nonclient area) could be re-used for #2238.
## PR Checklist
* [x] Closes#531, #3411
* [x] I work here
* [n/a] Tests added/passed 😭
* [x] Requires documentation to be updated
## Validation Steps Performed
* Manually tested both the NonClientIslandWindow and the IslandWindow.
* Cherry-pick commit 8e56bfe
* Don't draw the tab strip when maximized
(cherry picked from commit bac4be7c0f3ed1cdcd4f9ae8980fc98103538613)
* Fix the vista window flash for the NCIW
(cherry picked from commit 7d3a18a893c02bd2ed75026f2aac52e20321a1cf)
* Some code cleanup for review
(cherry picked from commit 9e22b7730bba426adcbfd9e7025f192dbf8efb32)
* A tad bit more notes and cleanup
* Update schema, docs
* Most of the PR comments
* I'm not sure this actually works, so I'm committing it to revert it and check
* Update some comments that were lost.
* Fix a build break?
* oh no
388b975663