cue/format: add test for incorrect formatting

A recent CL https://cuelang.org/cl/1170966 fixed up list element
indentation, but accidentally introduced a regression causing alignment
issues between fields in certain cases.

This CL adds a test indicating various cases in which the alignment is
now incorrect.

Signed-off-by: Noam Dolovich <noam.tzvi.dolovich@gmail.com>
Change-Id: I328f137d7e095a18cd0d91f57739f30b8f71d990
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1193255
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cue/format/testdata/expressions.golden

@@ -269,4 +269,13 @@ import "list"
 	o: [{}]
 	o: [{}]
 	o: [{}]
+
+	p:         1
+	p: p & {p: 2}
+	q:         1
+	q: q | {q: 2}
+	r:                1
+	r: b & [1, 2, {a: 4}]
+	s: [string]: [string]: a
+	s: [string]: {s:       string}
 }

cue/format/testdata/expressions.input

@@ -266,4 +266,13 @@ import "list"
     o: [ {}]
     o: [{} ]
     o: [ {} ]
+
+    p: 1
+    p: p & {p: 2}
+    q: 1
+    q: q | {q: 2}
+    r: 1
+    r: b & [1, 2, {a: 4}]
+    s: [string]: [string]: a
+    s: [string]: {s: string}
 }