x-pack/plugin/core: rename double_metrics template (#103033)

* x-pack/plugin/core: rename double_metrics template

Rename double_metrics to float_metrics, and create
a new double_metrics (with lower priority) that
has no match_mapping_type. The new one is intended
to be used with the dynamic_templates request
parameter.

Author: axw

docs/changelog/103033.yaml

@@ -0,0 +1,5 @@
+pr: 103033
+summary: "X-pack/plugin/core: rename `double_metrics` template"
+area: Data streams
+type: enhancement
+issues: []

x-pack/plugin/apm-data/src/yamlRestTest/resources/rest-api-spec/test/10_apm.yml

@@ -175,7 +175,7 @@ setup:
               full_name: double_metric
               mapping:
                 double_metric:
-                  type: float
+                  type: double
                   index: false
             summary_metric:
               full_name: summary_metric

x-pack/plugin/core/template-resources/src/main/resources/[email protected]

@@ -12,14 +12,22 @@
           }
         },
         {
-          "double_metrics": {
+          "float_metrics": {
             "match_mapping_type": "double",
             "mapping": {
               "type": "float",
               "index": false
             }
           }
         },
+        {
+          "double_metrics": {
+            "mapping": {
+              "type": "double",
+              "index": false
+            }
+          }
+        },
         {
           "histogram_metrics": {
             "mapping": {