chore: [release-3.1.x] docs: Recommended quickstart changes + Upgrade

[grafanabot]

Backport ef947ee from #13747

---

These changes were made to fix some of the issues found in: #13725

As well as this a general clean-up of Sandbox syntax so the markdown is less convoluted. I have also updated the Quickstart to Loki 3.1 and changed Alloy back to production due to a fix in 1.2.

Sandbox in dev: https://killercoda.com/grafana-dev-testing/course/loki/loki-quickstart
(Note that due to the demo pulling from the main branch of Loki, you will not see the newly updated containers for Loki or Alloy). I have tested these locally. If you would like to test within the sandbox you can run this command when pulling the docker-compose"

wget https://raw.githubusercontent.com/grafana/loki/recommended-quickstart-changes/examples/getting-started/loki-config.yaml -O loki-config.yaml
wget https://raw.githubusercontent.com/grafana/loki/recommended-quickstart-changes/examples/getting-started/alloy-local-config.yaml -O alloy-local-config.yaml
wget https://raw.githubusercontent.com/grafana/loki/recommended-quickstart-changes/examples/getting-started/docker-compose.yaml -O docker-compose.yaml

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR