[BUG] Rename field processor does not work with object/nested fields about opensearch

[dblock]

@LantaoJin Want to turn this into a (failing) YAML REST test?

[mch2]

looks related to search pipelines - @msfroh mind taking a look?

[msfroh]

This is a perfect example where a search pipeline processor has diverged from the mirrored ingest pipeline processor, where #13587 will help us use a single implementation.

Right now, the search pipeline processor does not resolve dot-paths to look at object/nested fields, whereas the ingest processor does.

We could go for a short-term fix that improves the search pipeline processor.

Alternatively, we can go for the longer-term solution of implementing #13587, to ensure that the ingest and search pipelines have identical capabilities.

[peternied]

[Triage - attendees 1 2 3]
@LantaoJin Thanks for creating this issue, what do you think about creating a pull request to fix this issue?