Remove dependency on Apache Nightlies download server

As seen in #420 , the Apache Nightlies download server is not a stable place to rely on for our CRDs and Helm Charts to be downloaded from.

Moving the CRDs and Helm Charts is a separate issue, but luckily both will be transparent to users as they will be using the same URLs as before.

The goal is that we won't have to store the CRDs or helm charts outside of the official release folder. Users will be directed to the official release folder while using convenient URLs redirected by the solr-site htaccess file.

まず #420 を確認し、現在の CRD と Helm chart のダウンロード URL を追跡します。solr-site の htaccess リダイレクトと公式の release フォルダーを調査します。既存の便利な URL が引き続き機能し、アーティファクトがそのフォルダーの外部に保存されなくなれば完了です。

索引モデルが issue の本文から書いたものです。