Separable module configuration -- without the bugs this time (#23703)

Currently, module configurations are inconsistent because modulefiles are generated with the configs for the active environment, but are shared among all environments (and spack outside any environment).

This PR fixes that by allowing Spack environments (or other spack config scopes) to define additional sets of modules to generate. Each set of modules can enable either lmod or tcl modules, and contains all of the previously available module configuration. The user defines the name of each module set -- the set configured in Spack by default is named "default", and is the one returned by module manipulation commands in the absence of user intervention.

As part of this change, the module roots configuration moved from the config section to inside each module configuration.

Additionally, it adds a feature that the modulefiles for an environment can be configured to be relative to an environment view rather than the underlying prefix. This will not be enabled by default, as it should only be enabled within an environment and for non-default views constructed with separate projections per-spec.

etc/spack/defaults/config.yaml

@@ -33,13 +33,6 @@ config:
   template_dirs:
     - $spack/share/spack/templates
 
-
-  # Locations where different types of modules should be installed.
-  module_roots:
-    tcl:    $spack/share/spack/modules
-    lmod:   $spack/share/spack/lmod
-
-
   # Temporary locations Spack can try to use for builds.
   #
   # Recommended options are given below.

etc/spack/defaults/linux/modules.yaml

@@ -14,8 +14,9 @@
 #   ~/.spack/modules.yaml
 # -------------------------------------------------------------------------
 modules:
-  prefix_inspections:
-    lib:
-      - LD_LIBRARY_PATH
-    lib64:
-      - LD_LIBRARY_PATH
+  default:
+    prefix_inspections:
+      lib:
+        - LD_LIBRARY_PATH
+      lib64:
+        - LD_LIBRARY_PATH

etc/spack/defaults/modules.yaml

@@ -14,8 +14,7 @@
 #   ~/.spack/modules.yaml
 # -------------------------------------------------------------------------
 modules:
-  enable:
-    - tcl
+  # Paths to check when creating modules for all module sets
   prefix_inspections:
     bin:
       - PATH
@@ -34,6 +33,20 @@ modules:
     '':
       - CMAKE_PREFIX_PATH
 
-  lmod:
-    hierarchy:
-      - mpi
+  # These are configurations for the module set named "default"
+  default:
+    # These values are defaulted in the code. They are not defaulted here so
+    # that we can enable backwards compatibility with the old syntax more
+    # easily (old value is in the config yaml, config:module_roots)
+    # Where to install modules
+    # roots:
+    #  tcl:    $spack/share/spack/modules
+    #  lmod:   $spack/share/spack/lmod
+    # What type of modules to use
+    enable:
+      - tcl
+
+    # Default configurations if lmod is enabled
+    lmod:
+      hierarchy:
+        - mpi