support for mimir proxy authentication

[dmalagoli-dylog]

This helm chart shows these same options also present in the original chart,

https://github.com/kubecost/cost-analyzer-helm-chart/blob/develop/cost-analyzer/values.yaml#L51-L67

but then the templates for the proxy are missing inside it.

This makes it impossible, for example, to use an authenticated external multi-tenant Mimir.

For example, this command does not spawn any nginx, and reports errors in autenticating with Mimir (real data removed)

helm upgrade --install kubecost-cloud kubecost-cloud-agent/kubecost-cloud-agent \
--namespace kubecost-cloud --create-namespace \
-f https://raw.githubusercontent.com/kubecost/kubecost-cloud-agent/main/values-cloud-agent.yaml \
--set kubecostModel.fullImageName="gcr.io/kubecost1/cloud-agent:0.1.4" \
--set cloudAgentKey="eyJ0ZWFtSWQiOiIzMmUzOTUyYS1mZDZhLTQxZWEtODlkYy0yMTYzMTc1YTdlMzYifQ==" \
--set cloudAgentClusterId="cluster-01" \
--set cloudReportingServer="ingress.app.kubecost.com:443" \
--set networkCosts.enabled=true \
--set global.mimirProxy.enabled=true \
--set global.prometheus.enabled=false \
--set global.prometheus.fqdn=https://mimir.****/prometheus \
--set global.mimirProxy.mimirEndpoint=https://mimir.**** \
--set global.mimirProxy.orgIdentifier=1 \
--set global.mimirProxy.basicAuth.username=**** \
--set global.mimirProxy.basicAuth.password=****

Request Error: Prometheus communication error: 401 (Unauthorized) URL: 'https://mimir.*****/prometheus/api/v1/query?query=sum%28increase%28kubecost_pod_network_egress_bytes_total%7Binternet%3D%22false │
│ ' Query: 'sum(increase(kubecost_pod_network_egress_bytes_total{internet="false", sameZone="false", sameRegion="false", }[2m] )) by (namespace,pod_name,cluster_id) / 1024 / 1024 / 1024' │
│ Parse Error: Prometheus communication error: sum(increase(kubecost_pod_network_egress_bytes_total{internet="false", sameZone="false", sameRegion="false", }[2m] )) by (namespace,pod_name,cluster_id) / 102 │
│ for Query: sum(increase(kubecost_pod_network_egress_bytes_total{internet="false", sameZone="false", sameRegion="false", }[2m] )) by (namespace,pod_name,cluster_id) / 1024 / 1024 / 1024