Remove Client.prepareIndex(index, type, id) method

[romseygeek]

As types are no longer used in index requests, we can remove the type parameter
from prepareIndex methods in the Client interface. However, just changing the signature
of prepareIndex(index, type, id) to prepareIndex(index, id) risks confusion when
upgrading with the previous (now removed) prepareIndex(index, type) method -
just changing the dependency version of java code would end up silently changing the
semantics of the method call. Instead we should just remove this method entirely, and
replace it by calling prepareIndex(index).setId(id)

[elasticmachine]

Pinging @elastic/es-core-infra (:Core/Infra/Transport API)

[elasticmachine]

Pinging @elastic/es-distributed (:Distributed/CRUD)

[romseygeek]

@elasticmachine run elasticsearch-ci/2

[rjernst]

LGTM. Note on terminology: the change here is not to the "transport client", as that has been removed. This is to the Client interface, which is essentially now just the node client (the client nodes use to communicate with each other, over the transport protocol, but sometimes also does local node requests).

[romseygeek]

Note on terminology: the change here is not to the "transport client", as that has been removed. This is to the Client interface, which is essentially now just the node client (the client nodes use to communicate with each other, over the transport protocol, but sometimes also does local node requests).

Thanks @rjernst, I've updated the description and title accordingly