chore: migrate to coder/websocket 1.8.12 (#15898)

Migrates us to `coder/websocket` v1.8.12 rather than `nhooyr/websocket` on an older version.

Works around https://github.com/coder/websocket/issues/504 by adding an explicit test for `xerrors.Is(err, io.EOF)` where we were previously getting `io.EOF` from the netConn.

vpn/client.go

@@ -7,7 +7,6 @@ import (
 	"net/url"
 
 	"golang.org/x/xerrors"
-	"nhooyr.io/websocket"
 	"tailscale.com/net/dns"
 	"tailscale.com/wgengine/router"
 
@@ -20,6 +19,7 @@ import (
 	"github.com/coder/coder/v2/tailnet"
 	"github.com/coder/coder/v2/tailnet/proto"
 	"github.com/coder/quartz"
+	"github.com/coder/websocket"
 )
 
 type Conn interface {

vpn/client_test.go

@@ -12,7 +12,6 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/mock/gomock"
-	"nhooyr.io/websocket"
 	"tailscale.com/net/dns"
 	"tailscale.com/tailcfg"
 
@@ -24,6 +23,7 @@ import (
 	"github.com/coder/coder/v2/tailnet/tailnettest"
 	"github.com/coder/coder/v2/testutil"
 	"github.com/coder/coder/v2/vpn"
+	"github.com/coder/websocket"
 )
 
 func TestClient_WorkspaceUpdates(t *testing.T) {