Fix module support for oneapi compilers (#28901)

Updates to improve Spack-generated modules for Intel oneAPI compilers:

* intel-oneapi-compilers set CC etc.
* Add a new package intel-oneapi-compilers-classic which can be used to
  generate a module which sets CC etc. to older compilers (e.g. icc)
* lmod module logic now updated to treat the intel-oneapi-compilers*
  packages as compilers

lib/spack/spack/modules/lmod.py

@@ -196,6 +196,14 @@ def provides(self):
         if self.spec.name == 'llvm-amdgpu':
             provides['compiler'] = spack.spec.CompilerSpec(str(self.spec))
             provides['compiler'].name = 'rocmcc'
+        # Special case for oneapi
+        if self.spec.name == 'intel-oneapi-compilers':
+            provides['compiler'] = spack.spec.CompilerSpec(str(self.spec))
+            provides['compiler'].name = 'oneapi'
+        # Special case for oneapi classic
+        if self.spec.name == 'intel-oneapi-compilers-classic':
+            provides['compiler'] = spack.spec.CompilerSpec(str(self.spec))
+            provides['compiler'].name = 'intel'
 
         # All the other tokens in the hierarchy must be virtual dependencies
         for x in self.hierarchy_tokens: