Fix rally-annotations index creation

Addresses https://github.com/elastic/rally/issues/1746.

The following naive fix reveals more problems:

diff --git a/esrally/resources/annotation-template.json b/esrally/resources/annotation-template.json
index 540bc589..fa62eaa2 100644
--- a/esrally/resources/annotation-template.json
+++ b/esrally/resources/annotation-template.json
@@ -1,6 +1,7 @@
 {
   "settings": {
-    "number_of_shards": 1
+    "index": {
+    }
   },
   "mappings": {
     "dynamic_templates": [

Output:

(.venv) grzegorz:elastic/rally% esrally add annotation --configuration-name=nightly-staging --track=elastic/security --message="test" --race-timestamp=20230712T000000Z

    ____        ____
   / __ \____ _/ / /_  __
  / /_/ / __ `/ / / / / /
 / _, _/ /_/ / / / /_/ /
/_/ |_|\__,_/_/_/\__, /
                /____/

[ERROR] Cannot add. module 'elasticsearch' has no attribute 'helpers'.

Stack trace:

2023-07-12 06:35:27,969 -not-actor-/PID:59902 esrally.rally ERROR A fatal error occurred while running subcommand [add].
Traceback (most recent call last):
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/metrics.py", line 107, in guarded
    return target(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/grzegorz/Documents/src/elastic/rally/.venv/lib/python3.11/site-packages/elasticsearch/_sync/client/utils.py", line 395, in wrapped
    raise ValueError(
ValueError: Couldn't merge 'body' with other parameters as it wasn't a mapping. Instead of using 'body' use individual API parameters

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/rally.py", line 1100, in dispatch_sub_command
    dispatch_add(cfg)
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/rally.py", line 865, in dispatch_add
    metrics.add_annotation(cfg)
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/metrics.py", line 1305, in add_annotation
    race_store(cfg).add_annotation()
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/metrics.py", line 1655, in add_annotation
    return self.es_store.add_annotation()
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/metrics.py", line 1777, in add_annotation
    self.client.create_index(index="rally-annotations", body=body)
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/metrics.py", line 71, in create_index
    return self.guarded(self._client.indices.create, index=index, body=body, ignore=400)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/grzegorz/Documents/src/elastic/rally/esrally/metrics.py", line 165, in guarded
    except elasticsearch.helpers.BulkIndexError as e:
           ^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'elasticsearch' has no attribute 'helpers'

Therefore the problem is not only the missing index object in annotations-template.json which is what https://github.com/elastic/rally/issues/1746 suggests but also upgraded Python Elasticsearch client is more strict when evaluating body parameter in index create method.

This PR addresses the problem by aligning rally-annotations index creation handling with other indices, i.e. by using rally-annotations index template. This simplicity comes at a cost of slightly "wasteful" configuration if users decided to increase datastore.number_of_shards setting (rally-annotations is tiny).

I've tested the change in staging environment:

DELETE rally-annotations
esrally add annotation ...

elastic / rally

Fix rally-annotations index creation #1747