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/dumpvars.go

@@ -249,7 +249,7 @@ func runMakeProductConfig(ctx Context, config Config) {
 	env := config.Environment()
 	// Print the banner like make does
 	if !env.IsEnvTrue("ANDROID_QUIET_BUILD") {
-		ctx.Writer.Print(Banner(make_vars))
+		fmt.Fprintln(ctx.Writer, Banner(make_vars))
 	}
 
 	// Populate the environment