[TEST] parse yaml responses too through ObjectPath rather than only json responses

No need to match against yaml responses via regexes in REST tests, yaml responses can be properly parsed via ObjectPath instead. Few REST tests need to be updated accordingly.

rest-api-spec/src/main/resources/rest-api-spec/test/cat.aliases/20_headers.yaml

@@ -17,12 +17,8 @@
       headers:
         Accept: application/yaml
 
-  - match:
-      $body: |
-        /^---\n
-          -\s+alias:\s+"test_alias"\s+
-              index:\s+"test"\s+
-              filter:\s+"-"\s+
-              routing.index:\s+"-"\s+
-              routing.search:\s+"-"\s+$/
-
+  - match: {0.alias: test_alias}
+  - match: {0.index: test}
+  - match: {0.filter: "-"}
+  - match: {0.routing\.index: "-"}
+  - match: {0.routing\.search: "-"}

rest-api-spec/src/main/resources/rest-api-spec/test/cat.aliases/30_yaml.yaml

@@ -17,13 +17,8 @@
       cat.aliases:
         format: yaml
 
-  - match:
-      $body: |
-        /^---\n
-          -\s+alias:\s+"test_alias"\s+
-              index:\s+"test"\s+
-              filter:\s+"-"\s+
-              routing.index:\s+"-"\s+
-              routing.search:\s+"-"\s+$/
-
-
+  - match: {0.alias: test_alias}
+  - match: {0.index: test}
+  - match: {0.filter: "-"}
+  - match: {0.routing\.index: "-"}
+  - match: {0.routing\.search: "-"}

rest-api-spec/src/main/resources/rest-api-spec/test/get/50_with_headers.yaml

@@ -18,13 +18,9 @@
         type: _all
         id:   1
 
-  - match:
-      $body: |
-        /^---\n
-          _index:\s+\"test_1"\n
-          _type:\s+"test"\n
-          _id:\s+"1"\n
-          _version:\s+1\n
-          found:\s+true\n
-          _source:\n
-          \s+body:\s+"foo"\n$/
+  - match: {_index: "test_1"}
+  - match: {_type: "test"}
+  - match: {_id: "1"}
+  - match: {_version: 1}
+  - match: {found: true}
+  - match: { _source: { body: foo }}

test/framework/src/main/java/org/elasticsearch/test/rest/client/RestTestResponse.java

@@ -68,7 +68,7 @@ public class RestTestResponse {
             String contentType = response.getHeader("Content-Type");
             XContentType xContentType = XContentType.fromMediaTypeOrFormat(contentType);
             //skip parsing if we got text back (e.g. if we called _cat apis)
-            if (xContentType == XContentType.JSON) {
+            if (xContentType == XContentType.JSON || xContentType == XContentType.YAML) {
                 this.parsedResponse = ObjectPath.createFromXContent(xContentType.xContent(), body);
             }
         }