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## Summary of the Pull Request
This PR splits the anchored and unanchored tab switcher into two. The anchored tab switcher is now baked into `nextTab`/`prevTab`, and the unanchored tab switcher command is just named `tabSearch`. `tabSearch` takes no arguments. To reflect this distinction, `CommandPalette.cpp` now refers to one as `TabSwitchMode` and the other as `TabSearchMode`.
I've added a global setting named `useTabSwitcher` (name up for debate) that makes the Terminal use the anchored tab switcher experience for `nextTab` and `prevTab`.
I've also given the control the ability to detect <kbd>Alt</kbd> KeyUp events and to dispatch keybinding events. By listening for keybindings, the ATS can react to `nextTab`/`prevTab` invocations for navigation in addition to listening for <kbd>tab</kbd> and the arrow keys.
Closes#7178
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## PR Checklist
* [x] CLA signed.
* [x] Documentation updates: microsoftdocs/terminal#107
* [x] Schema updated.
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