Helm: Fix chart mTLS implementation

[DylanGuedes]

What this PR does / why we need it:
Fix mTLS capabilities on our grafana/loki chart for microservices through the following changes:

• Add a new ssl key to the nginxConfig section. When ssl is true we append ssl to the listen directives.
• Add a new schema key to the nginxConfig section. schema is http by default but can be https. It is used by nginx when creating loki component URLs. For instance, requests to /loki/v1/push use http by default, but by changing this, they can use https. Used for internal mTLS.
• Change internal nginx URLs to work for both, distributed and SSD modes
• Fix distributor service targetPort (missing metrics suffix)
• Add extraVolumes and extraVolumeMounts to canaries deployment. They're useful when configuring mTLS for canaries
• Chnage index_gateway to run mode=simple by default
• Add tail_proxy_url to the helmchar default values
• I'm also adding a new distributed-tls file to show users how to configure the helmchart to work with mTLS.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer: