encoding/jsonschema: fix type exclusion test

This test was added by https://cue-review.googlesource.com/c/cue/+/5648
but included a case that was later made an error in
https://cue-review.googlesource.com/c/cue/+/6302 (the self-contradictory
`allOf` case), thus meaning the rest of the test was not
actually checked.

We move that case into its own test, ensuring that the other
cases pass.

We also rename the `emptyanyof` because it is not actually
testing an empty anyOf, but rather an empty object _inside_
an anyOf.

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: Id01c93b9085bff7726e8042a8d039e0ee5fd7ceb
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1199398
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

encoding/jsonschema/testdata/impossibleallof.txtar

@@ -0,0 +1,10 @@
+-- type.json --
+{
+    "allOf": [
+        { "type": "object" },
+        { "type": "string" }
+    ]
+}
+-- out/decode/err --
+constraint not allowed because type string is excluded:
+    type.json:4:11

encoding/jsonschema/testdata/typedis.txtar

@@ -33,23 +33,13 @@
             "minimum": 3
         }
       ]
-    },
-    "empty": {
-        "allOf": [
-            { "type": "object" },
-            { "type": "string" }
-        ]
     }
   }
 }
--- out/decode/err --
-constraint not allowed because type string is excluded:
-    type.json:39:15
 -- out/decode/cue --
 // Main schema
 intOrString1?: int | string
 intOrString2?: int | string
-intOrString3?: string | int
-disjunction?:  string | int | int & >=3
-empty?:        _|_
+intOrString3?: (int | string) & (number | string)
+disjunction?:  (int | string) & (number | string) | int & >=3
 ...