A minor TSF refactoring (#17067)

Next in the popular series of minor refactorings:
Out with the old, in with the new!

This PR removes all of the existing TSF code, both for conhost and
Windows Terminal. conhost's TSF implementation was awful:
It allocated an entire text buffer _per line_ of input.
Additionally, its implementation spanned a whopping 40 files and
almost 5000 lines of code. Windows Terminal's implementation was
absolutely fine in comparison, but it was user unfriendly due to
two reasons: Its usage of the `CoreTextServices` WinRT API indirectly
meant that it used a non-transitory TSF document, which is not the
right choice for a terminal. A `TF_SS_TRANSITORY` document (-context)
indicates to TSF that it cannot undo a previously completed composition
which is exactly what we need: Once composition has completed we send
the result to the shell and we cannot undo this later on.
The WinRT API does not allow us to use `TF_SS_TRANSITORY` and so it's
unsuitable for our application. Additionally, the implementation used
XAML to render the composition instead of being part of our text
renderer, which resulted in the text looking weird and hard to read.

The new implementation spans just 8 files and is ~1000 lines which
should make it significantly easier to maintain. The architecture is
not particularly great, but it's certainly better than what we had.
The implementation is almost entirely identical between both conhost
and Windows Terminal and thus they both also behave identical.
It fixes an uncountable number of subtle bugs in the conhost TSF
implementation, as it failed to check for status codes after calls.
It also adds several new features, like support for wavy underlines
(as used by the Japanese IME), dashed underlines (the default for
various languages now, like Vietnamese), colored underlines,
colored foreground/background controlled by the IME, and more!

I have tried to replicate the following issues and have a high
confidence that they're resolved now:
Closes #1304
Closes #3730
Closes #4052
Closes #5007  (as it is not applicable anymore)
Closes #5110
Closes #6186
Closes #6192
Closes #13805
Closes #14349
Closes #14407
Closes #16180

For the following issues I'm not entirely sure if it'll fix it,
but I suspect it's somewhat likely:
#13681
#16305
#16817

Lastly, there's one remaining bug that I don't know how to resolve.
However, that issue also plagues conhost and Windows Terminal
right now, so it's at least not a regression:
* Press Win+. (emoji picker) and close it
* Move the window around
* Press Win+.

This will open the emoji picker at the old window location.
It also occurs when the cursor moves within the window.
While this is super annoying, I could not find a way to fix it.

## Validation Steps Performed
* See the above closed issues
* Use Vietnamese Telex and type "xin choaf"
  Results in "xin chào" ✅
* Use the MS Japanese IME and press Alt+`
  Toggles between the last 2 modes ✅
* Use the MS Japanese IME, type "kyouhaishaheiku", and press Space
  * The text is converted, underlined and the first part is
    doubly underlined ✅
  * Left/Right moves between the 3 segments ✅
  * Home/End moves between start/end ✅
  * Esc puts a wavy line under the current segment ✅
* Use the Korean IME, type "gksgks"
  This results in "한한" ✅
* Use the Korean IME, type "gks", and press Right Ctrl
  Opens a popup which allows you to navigate with Arrow/Tab keys ✅

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

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