[docs] Move OPA ecosystem pages to site top-level (#6198)

* We are having trouble managing the complexity of having ecosystem pages shown in the versioned area of the OPA docs site (see website: link ecosystem from edge #6170)
* We have invested in the OPA ecosystem data recently and it makes sense to make it more prominent.
* The data in the OPA Ecosystem is harder to use when nested in docs as some Hugo functions are unavailable to nested sections.

This PR implements a solution by:

* Pages that were under /docs/version/ecosystem, /docs/version/integrations etc have been moved to /ecosystem and /integrations.
* Redirects have been created for the old pages in the netlify config.

Signed-off-by: Charlie Egan <charlie@styra.com>