replace `mirrors.chaos-mesh.org` with github urls

[STRRL]

for example:

https://mirrors.chaos-mesh.org/v2.7.1/install.sh -> https://raw.githubusercontent.com/chaos-mesh/chaos-mesh/refs/tags/v2.7.1/install.sh

[g1eny0ung]

There's something tricky going on here:

• chaosctl and chaosd assets are pushed directly to the mirrors. We need to build them and publish them to release assets.
• Can we remove some old assets in https://chaos-mesh.org/docs/upgrade-to-2.0/ and https://chaos-mesh.org/docs/upgrade-from-2.1-to-2.2/? For example, the migrate.sh I think is rarely used now, we can create a new repo and save them in it, and point the docs to the archives (https://chaos-mesh-website-archived.netlify.app/docs/).

@STRRL @Andrewmatilde What do you guys think?