Terminal: Support exe/dll paths in the 'icon' setting

[fpintos]

Support exe/icon paths in the 'icon' setting of a profile

The icon setting of a profile should allow the path to an EXE or DLL to be specified, along with an optional ID for an icon resource in the file.

For example, I should be able to create a profile using icons from SHELL32:

    ...
    "icon": "c:\Windows\System32\SHELL32.dll,210",
    ...

Optionally, if the icon is missing and the executable from the command line has icons, pick the default icon, much like how the shell does.

[Karl-WE]

I agree. or things like "icon": "C:\Program Files\PowerShell\6-preview\pwsh.exe",

[DHowett-MSFT]

Yeah, it would be pretty cool if we did this.

[DHowett-MSFT]

Notes: Right now we're using the XAML resource loader to get at our icons. If we want to support EXE/other PE resources we'll need to fall back to a more win32-like resource loader. There are real benefits to the XAML one, such as _it choosing the right icon scale_ and supporting vector graphics and stuff like that. I've tagged it help-wanted.

[Karl-WE]

@DHowett-MSFT afaik not even the settings app in Windows uses SVG graphics but PNGs. I stumbled across them once. I see the point of having this more modern and getting rid of old ico restrictions.