Requirements and preferences should not define (non-git) versions (#37687)

Ensure that requirements `packages:*:require:@x` and preferences `packages:*:version:[x]`
fail concretization when no version defined in the package satisfies `x`. This always holds
except for git versions -- they are defined on the fly.

share/spack/gitlab/cloud_pipelines/stacks/data-vis-sdk/spack.yaml

@@ -6,9 +6,9 @@ spack:
     mesa:
       require: "+glx +osmesa +opengl ~opengles +llvm"
     libosmesa:
-      require: ^mesa +osmesa
+      require: "mesa +osmesa"
     libglx:
-      require: ^mesa +glx
+      require: "mesa +glx"
     ospray:
       require: "@2.8.0 +denoiser +mpi"
     llvm: