feat: use github.com/eic/eic-spack as local eic-spack repo

Instead of using the local eic-spack repo, we should use the github eic-spack repo. That centralizes and makes it easier for users to use the same package recipes.

.gitlab-ci.yml

@@ -9,7 +9,7 @@ variables:
   AFTERBURNER_VERSION: "v0.1.2"
 
   ## Spack github version, v0.18.1
-  SPACK_VERSION: "13e6f87ef6527954b152eaea303841978e83b992"
+  SPACK_VERSION: "v0.18.1"
   ## Space-separated list of spack cherry-picks
   SPACK_CHERRYPICKS: "adc9f887eac78a81bb8189d603f4dc45ed3509c1 5bd44a795c76a61f0f9fbfeedcf7e917a0bf40b0"
   ## Ref: https://github.com/spack/spack/commit/[hash]