Create a unified environment with build matrices for different compilers

[climbfuji]

Is your feature request related to a problem? Please describe.
We want a unified environment that covers all application and that can be installed easily for multiple compilers.

Describe the solution you'd like
Scan the various virtual environment packages and combine those that are needed. Remove the others. Use build matrices for compilers to install the unified environment for multiple compilers in a single directory tree.

We put together a list of packages and versions in https://docs.google.com/spreadsheets/d/1j31C2WrG3hNAQAKdey8CbOx9eek_kGMsUVuHeBUhamg/edit?usp=sharing, based on the four applications global-workflow, ufs-weather-model, ufs-srw-app, skylab.

Additional context
The spack stack setup-meta-modules script does handle multiple compiler+MPI combinations in one environment, at least for lmod modules. Not sure about tcl modules, but the sites using those (Gaea, Narwhal, Ubuntu 20, Red Hat 8) typically use only one compiler.

[climbfuji]

Completed!