run benchmark tests on small-metal runners (#10549)

## Problem
Ref: https://github.com/neondatabase/cloud/issues/23314

We suspect some inconsistency in Benchmark tests runs could be due to
different type of runners they are landed in.
To have that aligned in both terms: failure rates and benchmark results,
lets run them for now on `small-metal` servers and see the progress for
the tests stability.
 
## Summary of changes

.github/actionlint.yml

@@ -4,6 +4,7 @@ self-hosted-runner:
     - large
     - large-arm64
     - small
+    - small-metal
     - small-arm64
     - us-east-2
 config-variables:

.github/workflows/build_and_test.yml

@@ -242,7 +242,7 @@ jobs:
       statuses: write
       contents: write
       pull-requests: write
-    runs-on: [ self-hosted, small ]
+    runs-on: [ self-hosted, small-metal ]
     container:
       image: ${{ needs.build-build-tools-image.outputs.image }}-bookworm
       credentials:
@@ -1101,7 +1101,7 @@ jobs:
                 state: 'closed',
                 base: branch,
               });
-              
+
               const pr = pullRequests.data.find(pr => pr.merge_commit_sha === context.sha);
               const prNumber = pr ? pr.number : null;