Stop updating AutoSuggestBox on selection redux (#18010)

I wrote a big comment next to the changes I made.
This is a redo of #17961 which had various issues.

Closes #17916
Closes #18070 

## Validation Steps Performed
* Pressing Enter within the input line doesn't crash ✅
* Type "Cour" and pick Courier New, press Save = Saved ✅
* Pick any other font from the dropdown, press Save = Saved ✅
* Picking an option dismisses focus but not to the tab row ✅
* The first time after launching the SUI, when the setting is still
  unmodified, when you focus the box and pick an option,
  it'll unfocus the box ✅
* When the setting is unmodified, and you pick the default
  (Cascadia Mono), it'll still unfocus the box ✅

.github/actions/spelling/expect/expect.txt

@@ -1464,6 +1464,7 @@ QWER
 Qxxxxxxxxxxxxxxx
 qzmp
 RAII
+Ralph
 RALT
 rasterbar
 rasterfont
@@ -2013,6 +2014,7 @@ WHelper
 wic
 WIDTHSCROLL
 Widthx
+Wiggum
 wil
 WImpl
 WINAPI