* add read_ilm cluster privilege
Although managing ILM policies is best done using the
"manage" cluster privilege, it is useful to have read-only
views.
* adds `read_ilm` cluster privilege for viewing policies and status
* adds Explain API to the `view_index_metadata` index privilege
* add manage_ilm privileges
This commit does a few things
- moves ILM-specifc rest yaml tests into plugin/ilm/qa, and creates special
:plugin:ilm:qa:rest module to test them
- removes the with-security tests of the yaml tests since they are covered in
the rest tests now
- moves ChangePolicyforIndexIT into the qa/multi-node project since that test is
not currently running in main ilm since integTest is disabled
This PR renames the CRUD APIS for ILM
GET _ilm/<policy>, _ilm -> _ilm/policy/<policy>, _ilm/policy
PUT _ilm/<policy> -> _ilm/policy/<policy>
DELETE _ilm/<policy> -> _ilm/policy/<policy>
closes#34929.
ILM now only forces indices to become read only in the case of Shrink
and Force Merge actions, as these are most useful in cases where the
index is no longer being written to.
The qa tests with security haven't actually gone as far as testing security roles yet, so this is a start in the hopes of both bringing the tests into the ilm plugin