Document Chapel prereqs for other package managers

[jabraham17]

Our current prereqs are specific to the system package manager for various popular operating systems. However, other package managers may be more attractive to users; conda, Homebrew, MacPorts, flatpak, and spack all come to mind. While we distribute Chapel packages through spack and Homebrew, we do not for the others.

At a minimum, we should determine the right packages users need when building from source and document it. Ideally this is done within the existing apptainer/vagraant portability tests which generate the prereqs docs. Of the package managers I listed, I think we should focus on conda first because we already have users making use of it without the docs.

Ideally we will also provide packages through conda, MacPorts, and flatpak, but I think the from source prereqs are still useful