Create separate docker container image for spacetime install page

[jdetter]

We recently discovered that the docker container that we use for SpacetimeDB standalone was broken when we split the binaries up. I opened #2289 to fix that issue but the docker container on the website is still in a state where it needs an update.

Essentially what we'd like to do is use a separate docker container image on the install page which uses the "normal" SpacetimeDB installation process instead of just using standalone.

The docker container we're referencing is the one on this page: https://spacetimedb.com/install