playground: gosh: switch from Logf/Fatalf to TB, and related

This change makes most of the changes described in the final
proposal in https://v.io/i/1128 - namely, it makes all the
requisite API changes.

Things not done in this change:
- "Good PC" logging
- Printing Cmd stdout/stderr on failure

Those will be done in subsequent changes.

MultiPart: 8/9

Change-Id: I043f7ee0cc482d6bfd3ec93293bc1e3f9a9242f0
diff --git a/go/src/v.io/x/playground/builder/builder_v23_test.go b/go/src/v.io/x/playground/builder/builder_v23_test.go
index e282397..2351ee6 100644
--- a/go/src/v.io/x/playground/builder/builder_v23_test.go
+++ b/go/src/v.io/x/playground/builder/builder_v23_test.go
@@ -87,7 +87,7 @@
 // Tests the playground builder tool.
 func TestV23PlaygroundBuilder(t *testing.T) {
 	v23test.SkipUnlessRunningIntegrationTests(t)
-	sh := v23test.NewShell(t, v23test.Opts{})
+	sh := v23test.NewShell(t, nil)
 	defer sh.Cleanup()
 	sh.Pushd(sh.MakeTempDir())
 	defer sh.Popd()
@@ -139,7 +139,7 @@
 // successfully.
 func TestV23PlaygroundBundles(t *testing.T) {
 	v23test.SkipUnlessRunningIntegrationTests(t)
-	sh := v23test.NewShell(t, v23test.Opts{})
+	sh := v23test.NewShell(t, nil)
 	defer sh.Cleanup()
 	sh.Pushd(sh.MakeTempDir())
 	defer sh.Popd()