jsonnet: Introduce backend target for Simple Scalable deployment mode

[szuro]

What this PR does / why we need it:

This PR adds the backend target for Simple Scalable deployment mode.
It also changes the read target deployment mode from StatefulSet to Deployment as per docs:

-target=read - The read target is stateless and can be run as a Kubernetes Deployment that can be scaled automatically. It contains the following components: – Query front end – Queriers

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• CHANGELOG.md updated
  • If the change is worth mentioning in the release notes, add add-to-release-notes label
• 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

[CLAassistant]

All committers have signed the CLA.

[github-actions]

Trivy scan found the following vulnerabilities:

• HIGH openssl: Incorrect cipher key and IV length processing in libcrypto3 v3.1.3-r0. Fixed in v3.1.4-r0
• HIGH openssl: Incorrect cipher key and IV length processing in libssl3 v3.1.3-r0. Fixed in v3.1.4-r0

[JStickler]

[Docs team] Fixed a couple of typos in the documentation.

[szuro]

[Docs team] Fixed a couple of typos in the documentation.

Thanks for noticing!

[szuro]

Resolved by #13976