cue: make internal cue port main API implementation

- rm cue/*.go
- mv internal/legacy/cue/*.go cue/
- rename imports
- go

Change-Id: I553ce372ad457b1d73126b0a3f7be8224e415e80
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/6742
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/encoding/jsonschema/jsonschema.go b/encoding/jsonschema/jsonschema.go
index 6451157..9e81b73 100644
--- a/encoding/jsonschema/jsonschema.go
+++ b/encoding/jsonschema/jsonschema.go
@@ -31,9 +31,9 @@
 package jsonschema
 
 import (
+	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/token"
-	"cuelang.org/go/internal/legacy/cue"
 )
 
 // Extract converts JSON Schema data into an equivalent CUE representation.