Regenerate v5preview/opensearchapi for single-pass union decode

Regenerated output of the osgen union changes: merged single-pass decoders for
mget/msearch/indices-open success|error items, As<T>() accessors for aggregation
and suggest result unions, and buffer-aliasing UnmarshalJSON across all unions.

Signed-off-by: Sean Chittenden <sean.chittenden@crowdstrike.com>

Author: sean-

opensearch-openapi.yaml

@@ -66278,6 +66278,8 @@ components:
           properties:
             reload_exception:
               $ref: '#/components/schemas/_common___ErrorCause'
+          required:
+            - reload_exception
     nodes.reload_secure_settings___NodeReloadResponse:
       type: object
       properties: