fix: Run expect tests on Windows with conpty pseudo-terminal (#276)

This brings together a bunch of random, partially implemented packages for support of the new(ish) Windows [`conpty`](https://devblogs.microsoft.com/commandline/windows-command-line-introducing-the-windows-pseudo-console-conpty/) API - such that we can leverage the `expect` style of CLI tests, but in a way that works in Linux/OSX `pty`s and Windows `conpty`.

These include:
- Vendoring the `go-expect` library from Netflix w/ some tweaks to work cross-platform
- Vendoring the `pty` cross-platform implementation from [waypoint-plugin-sdk](b55c787a65/internal/pkg/pty)
- Vendoring the `conpty` Windows-specific implementation from [waypoint-plugin-sdk](b55c787a65/internal/pkg/conpty)
- Adjusting the `pty` interface to work with `go-expect` + the cross-plat version

There were several limitations with the current packages:
- `go-expect` requires the same `os.File` (TTY) for input / output, but `conhost` requires separate file handles
- `conpty` does not handle input, only output
- The cross-platform `pty` didn't expose the full set of primitives needed for `console`

Therefore, the following changes were made:
- Handling of `stdin` was added to the `conpty` interface
- We weren't using the full extent of the `go-expect` interface, so some portions were removed (ie, exec'ing a process) to simplify our implementation and make it easier to extend cross-platform
- Instead of `console` exposing just a `Tty`, it exposes an `InTty` and `OutTty`, to help encapsulate the difference on Windows (on Linux, these point to the same pipe)

Future improvements:
- The `isatty` implementation doesn't support accurate detection of `conhost` pty's without an associated process. In lieu of a more robust check, I've added a `--force-tty` flag intended for test case use - that forces the CLI to run in tty mode.
- It seems the windows implementation doesn't support setting a deadline. This is needed for the expect.Timeout API, but isn't used by us yet.

Fixes #241

cli/workspacecreate_test.go

@@ -1,5 +1,3 @@
-//go:build !windows
-
 package cli_test
 
 import (
@@ -7,6 +5,7 @@ import (
 
 	"github.com/coder/coder/cli/clitest"
 	"github.com/coder/coder/coderd/coderdtest"
+	"github.com/coder/coder/expect"
 	"github.com/coder/coder/provisioner/echo"
 	"github.com/coder/coder/provisionersdk/proto"
 	"github.com/stretchr/testify/require"
@@ -37,7 +36,7 @@ func TestWorkspaceCreate(t *testing.T) {
 		cmd, root := clitest.New(t, "workspaces", "create", project.Name)
 		clitest.SetupConfig(t, client, root)
 
-		console := clitest.NewConsole(t, cmd)
+		console := expect.NewTestConsole(t, cmd)
 		closeChan := make(chan struct{})
 		go func() {
 			err := cmd.Execute()