* mark legacy ES client types as deprecated
* expose es client to plugins and update mocks
* ElasticSearchClientMock --> ElasticsearchClientMock
* expose es client mocks
* expose es client via RequestHandlerContext
* convert test/plugin_functional/config into ts
* convert top_nav test into ts
* add an integration test for the es client
* update comments to refer to the new es client
* fix import paths. do not use extensions
temp
* update docs
* fix other refs
* add test for a custom client
* fix context
* add test for scoped client
* update docs
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