fix(@angular-devkit/core): retain order of types set in allOf, anyOf and oneOf when parsing schema

With this change we retain the order of types are declared in the schema.
Ex:
```json
"oneOf": [
  {
    "type": "boolean"
  },
  {
    "type": "string",
    "description": "The name of the migration to run."
  }
]
```

Currently this will result in:
```js
{ type: "string", types: ["string", "boolean"] }
```

This is because we use the order of types from the `allTypes` contant variable.https://github.com/angular/angular-cli/blob/a3a657f7e7c20eafd49dfe80ab8fad5a973be9b7/packages/angular_devkit/core/src/json/schema/utility.ts#L12

Now this will result in:
```js
{ type: "boolean", types: ["boolean", "string"] };
```

The CLI parser will iterate over each type and will set a value of true if `--migrate-only` option is provided.

Related test in the CLL parser

https://github.com/angular/angular-cli/blob/1d105eb5691e7a0cf08383f56334ed2dfced3ad3/packages/angular/cli/models/parser_spec.ts#L34

https://github.com/angular/angular-cli/blob/1d105eb5691e7a0cf08383f56334ed2dfced3ad3/packages/angular/cli/models/parser_spec.ts#L132-L138

Author: alan-agius4

packages/angular_devkit/core/src/json/schema/utility.ts

@@ -59,7 +59,7 @@ export function getTypesOfSchema(schema: JsonSchema): Set<string> {
   if (Array.isArray(schema.allOf)) {
     for (const sub of schema.allOf) {
       const types = getTypesOfSchema(sub as JsonObject);
-      potentials = new Set([...potentials].filter(p => types.has(p)));
+      potentials = new Set([...types].filter(t => potentials.has(t)));
     }
   }
 
@@ -69,7 +69,7 @@ export function getTypesOfSchema(schema: JsonSchema): Set<string> {
       const types = getTypesOfSchema(sub as JsonObject);
       options = new Set([...options, ...types]);
     }
-    potentials = new Set([...potentials].filter(p => options.has(p)));
+    potentials = new Set([...options].filter(o => potentials.has(o)));
   }
 
   if (Array.isArray(schema.anyOf)) {
@@ -78,7 +78,7 @@ export function getTypesOfSchema(schema: JsonSchema): Set<string> {
       const types = getTypesOfSchema(sub as JsonObject);
       options = new Set([...options, ...types]);
     }
-    potentials = new Set([...potentials].filter(p => options.has(p)));
+    potentials = new Set([...options].filter(o => potentials.has(o)));
   }
 
   if (schema.properties) {