Use spack develop instead of releases

[climbfuji]

Is your feature request related to a problem?

spack changed their procedures and they no longer merge the release branches back to develop. This makes it impossible to use a release and then pull in develop or newer releases. See spack/spack#51264 (comment) for a conversation on this.

Describe the solution you'd like

After #1741 was merged (and maybe before or after spack-stack v2 was released), switch from spack v1.0.1 to spack develop. We need to make sure that the few, yet important, differences are transferred over.

Additional context

n/a

[eap]

Removing from 2.0 release workspace, this seems like cleanup we can do after the release and in the meantime we can document how to sync to the latest spack releases where that is necessary.

[climbfuji]

Removing from 2.0 release workspace, this seems like cleanup we can do after the release and in the meantime we can document how to sync to the latest spack releases where that is necessary.

That's fine, we should make this update in spack-stack 2.1