Change TSFInputControl inputScope to AlphanumericHalfWidth

[YanceyChiew]

Modified the scope of input control, it used to be Text, now it is
AlphanumericHalfWidth. This input scope actually accepts any
characters, but English characters are preferred, and the soft keyboard
also displays English by default.

This should improve user friendliness for users using composition mode
input methods.

As a user who uses the composition mode input method, in applications
like windows terminal that should usually be input in English, it is
always required to manually switch to English mode by pressing Shift
before entering commands.

One keystroke is not a problem, but often for some reason there is no or
no successful switching, and additional more keystrokes are required to
clear the wrong input.

The input method that comes with windows will automatically switch to
English mode for a few programs such as conhost, but windows terminal is
not in this list.

This change should have no negative impact. Even if someone does tend to
use a shell oriented towards composition characters or non-alpha
letters, there should also were more users who in the same language are
more inclined to English characters shells, for example, cmd,
powershell, bash that comes with windows.

If there's any reason to have to keep the Text inputScope, maybe making
this setting customizable via settings.json would be a good idea, but
I don't see the need to do this, AlphanumericHalfWidth is perfect.

Closes #12731

[zadjii-msft]

You've got solid notes in #12731, so I'm cool with this. Thanks for taking the time to look into this! I know I sure learned something new 😄

[DHowett]

Thank you!

[ghost]

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[DHowett]

@msftbot merge this in 1 minute

[ghost]

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[ghost]

🎉Windows Terminal Preview v1.14.143 has been released which incorporates this pull request.:tada:

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