The current "Building Queries" and "Building Aggregations" pages are
located under the "Supported Apis" section because they are linked to
the "Search API" page.
It should instead be in a dedicated section: this commit adds a new
"Using Java Builders" section and renames few filenames in favor of
more meaningful names.
By making RestHighLevelClient Closeable, its close method will close the internal low-level REST client instance by default, which simplifies the way most users interact with the high-level client.
Its constructor accepts now a RestClientBuilder, which clarifies that the low-level REST client is internally created and managed.
It is still possible to provide an already built `RestClient` instance, but that can only be done by subclassing `RestHighLevelClient` and calling the protected constructor that accepts a `RestClient`. In such case a consumer has also to be provided, which controls what has to be done when the high-level client gets done.
Closes#26086
Nik Everett
Tanguy Leroux
Luca Cavanna