Add loki-distributed chart, extract Gateway

[rastislavs]

• added a copy of loki-distributed Helm chart, but without Gateway
• added a Gateway Helm chart (temporary, will be driven by code later)
• put all MLA components into a single namespace
• whole stack can be installed with ./deploy-seed.sh
• promtail still part of ./deploy-seed.sh but will be moved to a new ./deploy-user-cluster.sh soon

k get pods -A                                                                                                                      ✔  default ⎈ 
NAMESPACE              NAME                                               READY   STATUS    RESTARTS   AGE
cluster-xyz            mla-gateway-cf9d97c57-tm82t                        1/1     Running   0          18m
mla                    cassandra-0                                        1/1     Running   0          24m
mla                    cassandra-1                                        1/1     Running   0          23m
mla                    cassandra-2                                        1/1     Running   0          21m
mla                    grafana-748799d97d-s8snw                           1/1     Running   0          18m
mla                    loki-distributed-distributor-775f685cc6-fkz98      1/1     Running   0          20m
mla                    loki-distributed-ingester-0                        1/1     Running   0          20m
mla                    loki-distributed-memcached-chunks-0                2/2     Running   0          20m
mla                    loki-distributed-memcached-frontend-0              2/2     Running   0          20m
mla                    loki-distributed-memcached-index-queries-0         2/2     Running   0          20m
mla                    loki-distributed-memcached-index-writes-0          2/2     Running   0          20m
mla                    loki-distributed-querier-0                         1/1     Running   0          20m
mla                    loki-distributed-query-frontend-6cc54c4c8c-kp877   1/1     Running   0          20m
mla                    loki-distributed-table-manager-84956ff978-k5t46    1/1     Running   0          20m
promtail               promtail-4r5sk                                     1/1     Running   0          11m