chore(deps): Update renovate configuration for more automation

[paul1r]

What this PR does / why we need it:
This PR does the following:

• Enables monitoring of the current set of releases under maintenance. This monitoring is limited to security patching only (a global configuration), and individual items like go/helm/docker monitoring are explicitly disabled for these branches.
• Enables automatic approval and merging of minor and patch fixes for Go updates. We have had success with this over the past few months, and it is time to remove the human element from the workflow.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

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
• 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

[paul1r]

renovate-config-validator                       
 INFO: Validating renovate.json5
 INFO: Config validated successfully

Approach was tested with a test repository. It can not be tested with a forks of the Loki repo, as Renovate does not run against forks

[trevorwhitney]

Hooray 🎉