[DOC] Update Helm chart doc

[knylander-grafana]

Update the Helm chart documentation to address gaps in content and common questions.

Helm chart doc: #4326

pages to update:

• Helm chart doc, https://grafana.com/docs/helm-charts/tempo-distributed/next/get-started-helm-charts/
• Enterprise traces gateway, https://grafana.com/docs/enterprise-traces/latest/configure/gateway/

Related:

• https://github.com/grafana/enterprise-traces/issues/1122
• Update Helm chart for Alloy - https://github.com/grafana/tempo-squad/issues/440
• tempo-distributed helm install fails if gateway:enabled:true helm-charts#3427
• https://github.com/grafana/enterprise-traces/issues/814
• [DOC] Update overrides content in Helm chart to clarify configuration for new, legacy #3820

Tasks

Beta Give feedback

1. Evaluate helm chart doc to make sure steps are up to date
2. Evaluate if we have gaps
3. Provide some example configs
4. Add TLS info - Add doc about configuring TLS with Helm #4328
5. Clarify the different types of gateway used in Helm chart for GET (enterpriseGateway), Tempo (gateway: true), nginx
6. Use the collapse shortcode for headings that are optional (https://grafana.com/docs/writers-toolkit/write/shortcodes/#collapse)
7. Address issues found by FE walkthrough of Helm chart docs (see comments below)

[knylander-grafana]

Zach's PR to handle TLS with Helm - #4328

[hedss]

Just rough C&P from GET install today:

• 4 cores and 16GB memory (don't believe this, unless it's 4vCPU per core, and anti-affinitising components could actually fail here if there aren't enough nodes)
• Image tag shouldn't be set because for latest chart version options will be wrong, latest is always defined as App Version anyway)
• Don't need to enable enterpriseGateway if enterprise is enabled, not even sure this flag is still valid?
• Don't need to explicitly disable gateway (it's never on by default) anyway
• Minio isn't enabled by default so you don't need to disable it in the chart if not using it
• Add an example of both Tempo and GET gateways for ingress (it's not clear how these are different and has caused confusion). We should be very clear on what each does and how to configure it. I don't think we should be explicitly stating the Enterprise Gateway by default as this could add an ingress when only an internal cluster/shared VPC setup is required.

Worth checking the rest of the doc too for other things when we go through this.
cc @ayah-el @danstadler-pdx