🌱 chore: publish chart to rancher/charts

[salasberryfin]

What this PR does / why we need it:

Moving to rancher/charts as Helm chart repository instead of using turtles. This change adds a new script to publish and promote chart versions on demand (taken from other Rancher components such as hosted providers, fleet, etc.).

When the next release of rancher-turtles is published, we'll open a PR against rancher/charts to manually add all required definitions for the chart to be available. Once we validate that the chart is properly served, we can use the automated scripts for updating the version in subsequent releases.

This change removes the existing functionality that uses chart-releaser to publish Helm charts to the repository and use it to serve Helm chart downloads.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Update release documentation with chart release process.

Checklist:

• squashed commits into logical changes
• includes documentation
• adds unit tests
• adds or updates e2e tests

[salasberryfin]

Closing this as we will not be publishing to rancher/charts.