Replace ConhostConnection with ConptyConnection (#3461)

This commit deletes ConhostConnection and replaces it with
ConptyConnection. The ConptyConnection uses CreatePseudoConsole and
depends on winconpty to override the one from kernel32.

* winconpty must be packageable, so I've added GetPackagingOutputs.
   * To validate this, I added conpty.dll to the MSIX regression script.
* I moved the code from conpty-universal that deals with environment
  strings into the types library.

This puts us in a way better place to implement #2563, as we can now
separately detect a failure to launch a pseudoconsole, a failure to
CreateProcess, and an unexpected termination of the launched process.

Fixes #1131.

build/scripts/Test-WindowsTerminalPackage.ps1

@@ -82,6 +82,10 @@ Try {
             Throw "Failed to find cpprest_2_10.dll -- check the WAP packaging project"
         }
     }
+
+    If ($null -eq (Get-Item "$AppxPackageRootPath\conpty.dll" -EA:Ignore)) {
+        Throw "Failed to find conpty.dll -- check the wapproj and winconpty.vcxproj"
+    }
 } Finally {
     Remove-Item -Recurse -Force $AppxPackageRootPath
 }

src/cascadia/CascadiaPackage/CascadiaPackage.wapproj

@@ -59,18 +59,13 @@
     <ProjectReference Include="..\WindowsTerminal\WindowsTerminal.vcxproj" />
     <ProjectReference Include="..\..\host\exe\Host.EXE.vcxproj" />
   </ItemGroup>
-  <!-- Stomp the path to conhost.exe.
-    This task will copy OpenConsole.exe to the appx as conhost.exe, and place it
-    adjacent to WindowsTerminal.exe.
-   -->
+
   <Target Name="OpenConsoleStompSourceProjectForWapProject" BeforeTargets="_ConvertItems">
     <ItemGroup>
       <!-- Stomp all "SourceProject" values for all incoming dependencies to flatten the package. -->
       <_TemporaryFilteredWapProjOutput Include="@(_FilteredNonWapProjProjectOutput)" />
       <_FilteredNonWapProjProjectOutput Remove="@(_TemporaryFilteredWapProjOutput)" />
       <_FilteredNonWapProjProjectOutput Include="@(_TemporaryFilteredWapProjOutput)">
-        <!-- Override the filename for OpenConsole.exe (only) -->
-        <TargetPath Condition="'%(Filename)' == 'OpenConsole' and '%(Extension)' == '.exe'">conhost.exe</TargetPath>
         <!-- Blank the SourceProject here to vend all files into the root of the package. -->
         <SourceProject>
         </SourceProject>

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -459,12 +459,12 @@ namespace winrt::TerminalApp::implementation
 
         else
         {
-            auto conhostConn = TerminalConnection::ConhostConnection(settings.Commandline(),
-                                                                     settings.StartingDirectory(),
-                                                                     settings.StartingTitle(),
-                                                                     settings.InitialRows(),
-                                                                     settings.InitialCols(),
-                                                                     winrt::guid());
+            auto conhostConn = TerminalConnection::ConptyConnection(settings.Commandline(),
+                                                                    settings.StartingDirectory(),
+                                                                    settings.StartingTitle(),
+                                                                    settings.InitialRows(),
+                                                                    settings.InitialCols(),
+                                                                    winrt::guid());
             sessionGuid = conhostConn.Guid();
             connection = conhostConn;
         }