Fixes #4221 Extra modifiers f1 to f4 in v2net

[tznind]

Fixes

• Fixes @tznind when do you intend to add support to these combinations? With NetDriver all the combinations with the F1 is possible as you can see in the image. #4221

Proposed Changes/Todos

F1 key can be
<esc>OP

But if combined with modifier keys it can instead be:

<esc>[1;3P

This PR updates key parsing to support this sequence

• Support Alt+F1, Shift+F1 etc

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

[BDisp]

It's better to check if the console support VTS. In this case the field should be _isVirtualTerminal. Of course with v2win you have to get this from the STD_OUTPUT_HANDLE and verify if ENABLE_VIRTUAL_TERMINAL_PROCESSING is enabled. Alacritty has VTS enabled and if you only check for Environment.GetEnvironmentVariable ("WT_SESSION") is { } || Environment.GetEnvironmentVariable ("VSAPPIDNAME") != null; it won't support true colors because you'll force 16 colors. With v2net VTS is always enabled by itself, so true color is always true in Unix like system and in Windows depends of the build version. The problem is check for VTS in this class. On my PR that I reverted I did a call to WindowsOutput to get the internal field IsVirtualTerminal, but you probably have another better solution for this. In Windows also always check the OS version build.

[tznind]

This is not in diff I think, I revert that accidental commit

[BDisp]

This is not in diff I think, I revert that accidental commit

I saw again and it was reverted, sorry. Good choice to assume they assume true colors at start. After start the app they are assumed or not accordingly with what the console supports.