The Java API documentation for index administration currenty is wrong because
the PutMappingRequestBuilder#setSource(Object... source) an
CreateIndexRequestBuilder#addMapping(String type, Object... source) methods
delegate to methods that check that the input arguments are valid key/value
pairs. This changes the docs so the java api code examples are included from
documentation integration tests so we detect compile and runtime issues earlier.
Closes#28131
ae912cbde4