cue/format: some tweaks

Always keep tabs used for indentation and explicitly
expand. This fixes some alignment issues.

This also prepares for having better eval output.

The default for single-element objects without
position information is now to not simplify.

Change-Id: I47546bce433cf99e2fc153540591cea51841b24c
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2165
Reviewed-by: Marcel van Lohuizen <mpvl@google.com>
diff --git a/internal/third_party/yaml/testdata/merge.out b/internal/third_party/yaml/testdata/merge.out
index e3edf5a..b8ed7a4 100644
--- a/internal/third_party/yaml/testdata/merge.out
+++ b/internal/third_party/yaml/testdata/merge.out
@@ -1,16 +1,18 @@
 // From http://yaml.org/type/merge.html
 // Test
-anchors list: [{
-	x: 1
-	y: 2
-}, {
-	x: 0
-	y: 2
-}, {
-	r: 10
-}, {
-	r: 1
-}]
+anchors: {
+	list: [{
+		x: 1
+		y: 2
+	}, {
+		x: 0
+		y: 2
+	}, {
+		r: 10
+	}, {
+		r: 1
+	}]
+}
 // All the following maps are equal:
 plain: {
 	// Explicit keys