Add auto_expand_replicas to joins track

[gareth-ellis]

The behaviour of auto_expand_replicas has changed which means that even in IT tests, we default to having a single replica. This unblocks the IT tests and also adds a new option to control the auto_expand_replicas behaviour for lookup indices

[fressi-elastic]

LGTM

[github-actions]

💔 All backports failed

Status	Branch	Result
❌	8.15	Backport failed because of merge conflicts You might need to backport the following PRs to 8.15: - Properly map the rally.doc_size and rally.message_size fields in elastic/logs track (#716) - Also propagate synthetic_source_keep if set to none (#715) - Exclude msmarco from IT tests (#708)

Manual backport

To create the backport manually run:

backport --pr 727

Questions ?

Please refer to the Backport tool documentation and see the Github Action logs for details

[esbenchmachine]

@gareth-ellis
A backport is pending for this PR. Please add all required vX.Y version labels.

• If it is intended for the current Elasticsearch release version, apply the corresponding version label.
• If it also supports past released versions, add those labels too.
• If it only targets a future version, wait until that version label exists and then add it.
  (Each rally-tracks version label is created during the feature freeze of a new Elasticsearch branch).

Backporting entails:

1. Ensure the correct version labels exist in this PR.
2. Ensure backport PRs have backport label and are passing tests.
3. Merge backport PRs (you can approve yourself and enable auto-merge).
4. Remove backport pending label from this PR once all backport PRs are merged.

Thank you!