Remove terminal.Writer

terminal.Writer is now just a wrapper around stdio.Stdout() without
any useful functionality.  Replace it with stdio.Stdout() as an
io.Writer.

Test: ui/terminal/status_test.go
Change-Id: I5bc5476afdca950b505642f0135a3af9d37fbe24

ui/build/config_test.go

@@ -22,14 +22,13 @@ import (
 	"testing"
 
 	"android/soong/ui/logger"
-	"android/soong/ui/terminal"
 )
 
 func testContext() Context {
 	return Context{&ContextImpl{
 		Context: context.Background(),
 		Logger:  logger.New(&bytes.Buffer{}),
-		Writer:  terminal.NewWriter(terminal.NewCustomStdio(&bytes.Buffer{}, &bytes.Buffer{}, &bytes.Buffer{})),
+		Writer:  &bytes.Buffer{},
 	}}
 }