CI(regress-tests): run tests on large-metal (#11634)

## Problem

Regression tests are more flaky on virtualised (`qemu-x64-*`) runners

See https://neondb.slack.com/archives/C069Z2199DL/p1744891865307769
Ref https://github.com/neondatabase/neon/issues/11627

## Summary of changes
- Switch `regress-tests` to metal-only large runners to mitigate flaky
behaviour

.github/workflows/_build-and-test-locally.yml

@@ -349,7 +349,7 @@ jobs:
       contents: read
       statuses: write
     needs: [ build-neon ]
-    runs-on: ${{ fromJSON(format('["self-hosted", "{0}"]', inputs.arch == 'arm64' && 'large-arm64' || 'large')) }}
+    runs-on: ${{ fromJSON(format('["self-hosted", "{0}"]', inputs.arch == 'arm64' && 'large-arm64' || 'large-metal')) }}
     container:
       image: ${{ inputs.build-tools-image }}
       credentials: