[Change Proposal] Support `esql_view` asset type

[kpollich]

Support a new esql_view asset type for ES|QL views. This would be an Elasticsearch asset type in a package's elasticearch/ directory.

For future extensibility, declaring ES|QL views as YML files would likely be best, e.g.

# packages/my_integration/elasticsearch/esql_views/my_view.yml
name: my_view
query: |
  FROM security_logs
  | WHERE event.kind == \"alert\"
  | STATS event_count = COUNT(), last_seen = MAX(@timestamp) BY `rule.name`"

Defining the views in YML allow us to extend the definition with additional metadata or configuration in the future.

[kpollich]

We should also support ES|QL views as an asset type in content packs. Does anything block us from doing that as part of this work @elastic/ecosystem?

[jsoriano]

Yeah, I think this could be added.