Restore support for pasting files

[lhecker]

TIL: You could Ctrl+V files into Windows Terminal and here I am,
always opening the context menu and selecting "Copy as path"... smh

This restores the support by adding a very rudimentary HDROP handler.
The flip side of the regression is that I learned about this and so
conhost also gets this now, because why not!

Closes #16627

Validation Steps Performed

• Single files can be pasted in WT and conhost ✅

[DHowett]

Hey, the WinRT API was doing something for us that we didn't have to worry too much about!

[lhecker]

Ackchyually, we had to do it manually:

terminal/src/cascadia/TerminalApp/TerminalPage.cpp

Lines 2620 to 2629 in 78de114

	// Windows Explorer's "Copy address" menu item stores a StorageItem in the clipboard, and no text.
	else if (data.Contains(StandardDataFormats::StorageItems()))
	{
	auto items = co_await data.GetStorageItemsAsync();
	if (items.Size() > 0)
	{
	auto item = items.GetAt(0);
	text = item.Path();
	}
	}

That's effectively the HDROP handler but with WinRT APIs. I removed it because I never realized that you could simply Ctrl+V a file into WT. The author of that code might not have known either because look at the comment on top of it: It only refers to the whacky "Copy address" menu item, and that one happens to actually contain a CF_UNICODETEXT and that's why I didn't port the HDROP handling into the Win32 code.

[DHowett]

we shouldn't use winrt::impl types directly. However, I don't love any of the other options. heh

[DHowett]

I removed it because I never realized that you could simply Ctrl+V a file into WT. The author of that code might not have known either because look at the comment on top of it: It only refers to the whacky "Copy address" menu item, and that one happens to actually contain a CF_UNICODETEXT and that's why I didn't port the HDROP handling into the Win32 code.

Ah, I see.