Set the "build_jobs" on concretization/generate for CI (#47660)

* Set the "build_jobs" on concretization/generate for CI

build_jobs also controls the concretization pool size. Set this
in the config section for CI generate.

This config is overwritten by build_job CI using the SPACK_BUILD_JOBS
environment variable. This implicitly will drop the default build
CPU request on all "default" grouped build jobs from (max) 16 to 8.

* Add default allocations for build jobs

* Add common jobs and concretize args to ci generate and rebuild

* CI: Specify parallel concretize and build jobs via argument

* Increase power and cray concretization limits

Lowering limits for these stacks creates timeout

lib/spack/spack/cmd/ci.py

@@ -17,6 +17,7 @@
 import spack.ci as spack_ci
 import spack.cmd
 import spack.cmd.buildcache as buildcache
+import spack.cmd.common.arguments
 import spack.config as cfg
 import spack.environment as ev
 import spack.hash_types as ht
@@ -116,6 +117,9 @@ def setup_parser(subparser):
     )
     generate.set_defaults(func=ci_generate)
 
+    spack.cmd.common.arguments.add_concretizer_args(generate)
+    spack.cmd.common.arguments.add_common_arguments(generate, ["jobs"])
+
     # Rebuild the buildcache index associated with the mirror in the
     # active, gitlab-enabled environment.
     index = subparsers.add_parser(
@@ -145,6 +149,7 @@ def setup_parser(subparser):
         help="stop stand-alone tests after the first failure",
     )
     rebuild.set_defaults(func=ci_rebuild)
+    spack.cmd.common.arguments.add_common_arguments(rebuild, ["jobs"])
 
     # Facilitate reproduction of a failed CI build job
     reproduce = subparsers.add_parser(
@@ -440,6 +445,9 @@ def ci_rebuild(args):
     if not verify_binaries:
         install_args.append("--no-check-signature")
 
+    if args.jobs:
+        install_args.append("-j{args.jobs}")
+
     slash_hash = spack_ci.win_quote("/" + job_spec.dag_hash())
 
     # Arguments when installing the root from sources