[DOCS] Relocate scriptless runtime document (#68916)

* Reallocate runtime document

Reallocate document `runtime-fields-scriptless` from `runtime-search-request` to `runtime-mapping-fields`

* Move runtime without script section

Move runtime without script section to under the dynamic runtime mapping section

* Fix snippet formatting and remove discrete heading.

* Update test snippet.

Co-authored-by: Adam Locke <adam.locke@elastic.co>

docs/reference/mapping/runtime.asciidoc

@@ -139,22 +139,48 @@ PUT my-index
 }
 ----
 
-You can update or remove runtime fields at any time. To replace an existing runtime field, add a new runtime field to the mappings with the same name. To remove a runtime field from the mappings, set the value of the runtime field to `null`:
-
- [source,console]
- ----
- PUT my-index/_mapping
- {
-   "runtime": {
-     "day_of_week": null
-   }
- }
- ----
+[[runtime-fields-scriptless]]
+==== Define runtime fields without a script
+You can define a runtime field in the mapping definition without a
+script. At query time, {es} looks in `_source` for a field with the same name
+and returns a value if one exists. If a field with the same name doesn’t
+exist, the response doesn't include any values for that runtime field.
+
+[source,console]
+----
+PUT my-index/
+{
+  "mappings": {
+    "runtime": {
+      "day_of_week": {
+        "type": "keyword"
+      }
+    }
+  }
+}
+----
 
 [[runtime-updating-scripts]]
-.Updating and removing runtime fields
-****
+==== Updating and removing runtime fields
+
+You can update or remove runtime fields at any time. To replace an existing
+runtime field, add a new runtime field to the mappings with the same name. To
+remove a runtime field from the mappings, set the value of the runtime field to
+`null`:
 
+[source,console]
+----
+PUT my-index/_mapping
+{
+ "runtime": {
+   "day_of_week": null
+ }
+}
+----
+//TEST[continued]
+
+.Downstream impacts
+****
 Updating or removing a runtime field while a dependent query is running can return
 inconsistent results. Each shard might have access to different versions of the
 script, depending on when the mapping change takes effect.
@@ -163,7 +189,6 @@ Existing queries or visualizations in {kib} that rely on runtime fields can
 fail if you remove or update the field. For example, a bar chart visualization
 that uses a runtime field of type `ip` will fail if the type is changed
 to `boolean`, or if the runtime field is removed.
-
 ****
 
 [[runtime-search-request]]
@@ -213,27 +238,6 @@ runtime field from a search request to the index mapping by moving the field
 definition from `runtime_mappings` in the search request to the `runtime`
 section of the index mapping.
 
-[[runtime-fields-scriptless]]
-==== Define runtime fields without a script
-You can define a runtime field in the mapping definition without a
-script. At query time, {es} looks in `_source` for a field with the same name
-and returns a value if one exists. If a field with the same name doesn’t
-exist, the response doesn't include any values for that runtime field.
-
-[source,console]
-----
-PUT my-index/
-{
-  "mappings": {
-    "runtime": {
-      "model_number": {
-        "type": "keyword"
-      }
-    }
-  }
-}
-----
-
 [[runtime-override-values]]
 === Override field values at query time
 beta::[]