use c6/7/8 runners

Author: kalverra

.github/workflows/cre-regression-system-tests.yaml

@@ -91,7 +91,7 @@ jobs:
             | map({
                 test_name: .value,
                 test_id: .key,
-                runs_on: "runs-on=\($run_id)-\(.key)-\($run_attempt)/cpu=8/ram=64/family=r6i+r7i+r8i/spot=co/image=ubuntu24-full-x64/extras=s3-cache",
+                runs_on: "runs-on=\($run_id)-\(.key)-\($run_attempt)/cpu=8/ram=16/family=c6i+c7i+c8i/spot=co/image=ubuntu24-full-x64/extras=s3-cache",
                 configs: ($per[.value] // "configs/workflow-gateway-capabilities-don.toml")
               })
           ')

.github/workflows/cre-system-tests.yaml

@@ -129,7 +129,7 @@ jobs:
             | to_entries
             | map(.value + {
                 test_id: .key,
-                runs_on: "runs-on=\($run_id)-\(.key)-\($run_attempt)/cpu=8/ram=64/family=r6i+r7i+r8i/spot=co/image=ubuntu24-full-x64/extras=s3-cache"
+                runs_on: "runs-on=\($run_id)-\(.key)-\($run_attempt)/cpu=8/ram=16/family=c6i+c7i+c8i/spot=co/image=ubuntu24-full-x64/extras=s3-cache"
               })
           ')