Add support for OSC 52 clipboard copies in conhost

[lhecker]

Description of the new feature

Windows Terminal supports OSC 52 and so conhost should too.

Proposed technical implementation details

This is super easy to do and only requires us to fill out this function:

terminal/src/host/outputStream.cpp

Lines 277 to 286 in 2d64a3a

	// Routine Description:
	// - Copies the given content to the clipboard.
	// Arguments:
	// - content - the text to be copied.
	// Return Value:
	// - <none>
	void ConhostInternalGetSet::CopyToClipboard(const wil::zwstring_view /*content*/)
	{
	// TODO
	}

To do so, we need to extend the Clipboard class to expose this function (in a more convenient way though):

terminal/src/interactivity/win32/clipboard.hpp

Line 38 in 2d64a3a

static void _copyToClipboard(UINT format, const void* src, size_t bytes);

(Note that you need to set Host.EXE as your startup project.)

[j4james]

I actually have a old branch with an implementation for this, but it wasn't as easy as you might imagine. As far as I understand, you can only access the clipboard from the main window thread, so I had to post a custom message from the CopyToClipboard handler to pass on the content to the Window::ConsoleWindowProc, and then set the clipboard from there. It all seemed a bit hacky, which is why I abandoned it, but maybe there's an easier solution that I'm missing.

See also #13408, which was kind of tracking this issue amongst other things.

[lhecker]

As far as I understand, you can only access the clipboard from the main window thread

Oh right! Yes, I think that's correct. Reading the clipboard without the HWND is possible but not writing it.