Get rid of using legacydata.RequestHandler in HTTPServer, /api/tsdb/query and pkg/expr
with the goal of deprecating /api/tsdb/query and remove it completely eventually. This is
the first step of cleaning up the HTTP API query endpoint.
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Alexander Emelin <frvzmb@gmail.com>
Refactor usage of legacy data contracts. Moves legacy data contracts
to pkg/tsdb/legacydata package.
Refactor pkg/expr to be a proper service/dependency that can be provided
to wire to remove some unneeded dependencies to SSE in ngalert and other places.
Refactor pkg/expr to not use the legacydata,RequestHandler and use
backend.QueryDataHandler instead.
