Create a Basic Core Search Service with indexing capability

Add a new search service at core level, implementation will be contributed by packages.

We want to be able to contribute a SearchClient with its associated indexes:

• SearchClient with an implementation class and connection options to access a search service (elastic, opensearch, ...)
• SearchIndex config to setup an index tied to a repository (settings and mappings)

We want to be able to

• have multiple index configurations per search client: typical multi-repo setup on an elastic cluster
• have multiple search clients: so we could split the elastic cluster or use mulltiple clients (elastic, opensearch ...) at the same time
• have multiple index configuration on the same repository: could be useful to have localized indexes for a repository

The Search client should provides:

• way to create index if not exists with mapping/settings
• way to drop index
• way to index/delete docs: indexDocuments(index, List<String> toDelete, List<JsonNode> toUpsert, boolean refresh)

Basic Search Service is focused on indexing with a opensearch 1.x implementation
for now this will part of core module (to be externalized on a package)