Find icon from shortcut target if shortcut doesn't specify it

[malxau]

Implements what I was suggesting in #6266 where if a shortcut doesn't
specify an icon, the shortcut target full path is used before searching
for a matching executable in the path.

References

Found due to not getting the right icon in conhost from the Yori
installer. It's fixed in the installer from
malxau/yori@5af366b
for all current users of conhost though, so this PR is just trying to
minimize surprises for the next guy.

Detailed Description of the Pull Request / Additional comments

I know conhost and shortcut settings aren't really the team's focus
which is why I'm doing this. I understand though if there's a better
way or there are factors that I hadn't considered. Note that the path
searching code is used when programs are launched without using a
shortcut, and it will match if the working directory of the shortcut is
the directory containing the executable.

Validation Steps Performed

Created a shortcut that didn't specify an icon to a binary that wasn't
in the path, and verified that the icon in the upper left of the console
window could resolve correctly when opening the shortcut. I'm not aware
of a way to get into this path (of launching via a shortcut to a command
line process) without replacing the system conhost, which is what I did
to verify it. In order to diagnose it, I used hardcoded DebugBreak()
since even ImageFileExecutionOptions didn't like running against conhost-
is there are better way to debug and test these cases without being so
invasive on the system?

Closes #6266

[miniksa]

In order to diagnose it, I used hardcoded DebugBreak() since even ImageFileExecutionOptions didn't like running against conhost - is there are better way to debug and test these cases without being so invasive on the system?

Not really, no. Conhost is gross to debug.

[miniksa]

I'm fine with this. It seems reasonable to look at this path for context. Thanks.

[DHowett]

Let's do this. Thanks @malxau!

[ghost]

Hello @DHowett!

Because this pull request has the AutoMerge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

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[DHowett]

Minor callout - there's this guy in our docs on debugging:

NOTE: conhost.exe already has a provision for a conditional DebugBreak() very early in the startup code if it was built in debug mode. Set HKCU\Console with DebugLaunch as a REG_DWORD with the value of 1.

[ghost]

🎉Windows Terminal Preview v1.1.1671.0 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes
• Store Download

[DHowett]

🎉 Once again, thanks for the contribution!

This pull request was included in a set of conhost changes that was just
released with Windows Insider Build 20161.