[Failure Store] ES|QL security tests (#125586) (#126857)

Some basic coverage for ES|QL security with failure store access. The
behavior w.r.t. status codes diverges quite a bit between ES|QL and
_search but not in any failure store specific way. ES|QL has the same
authorization behavior when querying multiple data streams without
failure store access in the mix.

Author: n1v0lg