cue: get rid of NewRuntime

It exposes an internal type that is no longer necessary.

Change-Id: Ia683a0986bc43a39bef751406f9e9e8529fc3b70
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9422
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Paul Jolly <paul@myitcv.org.uk>
diff --git a/cue/build.go b/cue/build.go
index 5900e89..e522765 100644
--- a/cue/build.go
+++ b/cue/build.go
@@ -177,12 +177,6 @@
 	})
 }
 
-// NewRuntime creates a *runtime.Runtime with builtins preloaded.
-func NewRuntime() *runtime.Runtime {
-	i := newIndex()
-	return i
-}
-
 // newIndex creates a new index.
 func newIndex() *runtime.Runtime {
 	return runtime.New()
diff --git a/internal/core/adt/eval_test.go b/internal/core/adt/eval_test.go
index e52677e..06143b4 100644
--- a/internal/core/adt/eval_test.go
+++ b/internal/core/adt/eval_test.go
@@ -22,10 +22,10 @@
 
 	"github.com/rogpeppe/go-internal/txtar"
 
-	"cuelang.org/go/cue"
 	"cuelang.org/go/internal/core/adt"
 	"cuelang.org/go/internal/core/debug"
 	"cuelang.org/go/internal/core/eval"
+	"cuelang.org/go/internal/core/runtime"
 	"cuelang.org/go/internal/core/validate"
 	"cuelang.org/go/internal/cuetest"
 	"cuelang.org/go/internal/cuetxtar"
@@ -49,7 +49,7 @@
 		test.ToDo = nil
 	}
 
-	r := cue.NewRuntime()
+	r := runtime.New()
 
 	test.Run(t, func(t *cuetxtar.Test) {
 		a := t.ValidInstances()
@@ -115,7 +115,7 @@
 		t.Fatal(instance.Err)
 	}
 
-	r := cue.NewRuntime()
+	r := runtime.New()
 
 	v, err := r.Build(instance)
 	if err != nil {
diff --git a/internal/core/export/export_test.go b/internal/core/export/export_test.go
index 43bd421..a47d92a 100644
--- a/internal/core/export/export_test.go
+++ b/internal/core/export/export_test.go
@@ -42,7 +42,7 @@
 		Update: cuetest.UpdateGoldenFiles,
 	}
 
-	r := cue.NewRuntime()
+	r := runtime.New()
 
 	test.Run(t, func(t *cuetxtar.Test) {
 		a := t.ValidInstances()
diff --git a/internal/core/export/extract_test.go b/internal/core/export/extract_test.go
index df76632..9d4ce97 100644
--- a/internal/core/export/extract_test.go
+++ b/internal/core/export/extract_test.go
@@ -18,11 +18,11 @@
 	"fmt"
 	"testing"
 
-	"cuelang.org/go/cue"
 	"cuelang.org/go/internal/core/adt"
 	"cuelang.org/go/internal/core/compile"
 	"cuelang.org/go/internal/core/eval"
 	"cuelang.org/go/internal/core/export"
+	"cuelang.org/go/internal/core/runtime"
 	"cuelang.org/go/internal/cuetest"
 	"cuelang.org/go/internal/cuetxtar"
 )
@@ -34,7 +34,7 @@
 		Update: cuetest.UpdateGoldenFiles,
 	}
 
-	r := cue.NewRuntime()
+	r := runtime.New()
 
 	test.Run(t, func(t *cuetxtar.Test) {
 		a := t.ValidInstances()
diff --git a/internal/core/export/value_test.go b/internal/core/export/value_test.go
index 7e7fc65..2312a5e 100644
--- a/internal/core/export/value_test.go
+++ b/internal/core/export/value_test.go
@@ -18,7 +18,6 @@
 	"fmt"
 	"testing"
 
-	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/internal/core/adt"
@@ -43,7 +42,7 @@
 		Skip:   exclude,
 	}
 
-	r := cue.NewRuntime()
+	r := runtime.New()
 
 	test.Run(t, func(t *cuetxtar.Test) {
 		a := t.ValidInstances()
diff --git a/pkg/internal/builtintest/testing.go b/pkg/internal/builtintest/testing.go
index 0f65167..98eaeaa 100644
--- a/pkg/internal/builtintest/testing.go
+++ b/pkg/internal/builtintest/testing.go
@@ -18,10 +18,10 @@
 	"fmt"
 	"testing"
 
-	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/format"
 	"cuelang.org/go/internal/core/eval"
 	"cuelang.org/go/internal/core/export"
+	"cuelang.org/go/internal/core/runtime"
 	"cuelang.org/go/internal/core/validate"
 	"cuelang.org/go/internal/cuetxtar"
 )
@@ -32,7 +32,7 @@
 		Name: name,
 	}
 
-	r := cue.NewRuntime()
+	r := runtime.New()
 
 	test.Run(t, func(t *cuetxtar.Test) {
 		a := t.ValidInstances()