Pass keyboard layout down to ConPTY and consider readding support for GetConsoleKeyboardLayoutName

### Description of the new feature

To help PowerShell with their `ToUnicode` usage we should pass down the keyboard layout to ConPTY so that their keyboard-layout hack works:
https://github.com/PowerShell/PSReadLine/blob/e87a265ef8d2c6c5498500deb155bf6258b34629/PSReadLine/PlatformWindows.cs#L1106-L1109

To avoid the need for such a workaround, we should readd support for the existing `GetConsoleKeyboardLayoutName` function. There's not really a good reason to not support it. It's also used by vim and probably others so it may be quite helpful.

### Proposed technical implementation details

_No response_

Start by tracing how ConPTY receives keyboard-layout information and how the existing GetConsoleKeyboardLayoutName function is handled. Review the PowerShell PlatformWindows.cs usage linked in the issue and consider Vim's reported use case. Done means ConPTY passes the layout needed by ToUnicode and the existing function is supported again.

Written by the indexing model from the issue text.