Site config updates and bug fixes for spack-stack-2.1

[climbfuji]

Is your feature request related to a problem?

For spack-stack-2.1, a few site configs need to be updated to address issues or complete work that didn't make it into spack-stack-2.0.

Describe the solution you'd like

• Hercules: Fix py-scipy build errors (in meson step) with Intel oneAPI compilers - @rickgrubin-noaa and @AlexanderRichert-NOAA
• Orion: Fix py-scipy build errors (in meson step) with Intel oneAPI compilers - @rickgrubin-noaa and @AlexanderRichert-NOAA
• Discover: Fix ectrans build errors (in cmake step) with GNU compilers - @rickgrubin-noaa and @climbfuji
• S4: move to tier2, update documentation and release tasklist issue template accordingly - @climbfuji
• Gaea C5: Move to tier2, update documentation and release tasklist issue template accordingly - @climbfuji
• Containers: Replace current spack ctr builds with a tier 1 site config for a container build that is more similar to how we install on bare-metal systems. @eap and @climbfuji with input from EPIC; Clean up as part of this work:
  • Revert spack-stack modifications of container builds in Spack engine code - @climbfuji
  • Remove spack stack ctr extension and associated unit tests - @climbfuji
  • Update documentation and GitHub actions for new container build - @eap

Additional context

See discussion (comments) in #1835 for some of the site config build errors encountered during the spack-stack-2.0 release.