EPIC: Migrate to using developer portal by default

[tolzhabayev]

Why?
Since we now have a proper URL you can use to link to dataplane documentation - we should migrate away from using github pages (github.io) and use the new URL instead.

DEV: https://grafana-dev.com/developers/dataplane/
PROD: https://grafana.com/developers/dataplane/

What to consider and how do we do this?

• Start by adjusting the inbound links to https://grafana.com/developers/dataplane/
• Stop publishing to github.io
• Redirect from github.io (if you want to)
• Adjust the build scripts and remove the parent / landing page
• Remove github.io publishing workflows
• At some point in the future disable github pages

Nice to have

• Add "Tools & Examples" sections and page to the side navigation to not loose this links once we get rid of the dataplane specific landing page.

Tasks

Beta Give feedback

1. Adjust inbound links to https://grafana.com/developers/dataplane/
2. Adjust the build scripts and remove the parent / landing page (similar to Removing landing page and reshuffling docs plugin-tools#359)
3. Add rudderstack tracking #33
   documentation +1
4. Add "back to dev portal" link - same as Docs: Add portal home links plugin-tools#377

Nice To Have

Beta Give feedback

1. Add "Tools & Examples" sections and page to the side navigation to not loose this links once we get rid of the dataplane specific landing page.

[tolzhabayev]

@yesoreyeram I can help out with this if you want - let me know.