add credentials for pulling containers for the jobs (#10987)

Ref: https://github.com/neondatabase/cloud/issues/24939

## Problem
I found that we are missing authorization for some container jobs, that
will make them use anonymous pulls. It's not an issue for now, with high
enough limits, but that could be an issue when new limits introduced in
DockerHub (10 pulls / hour)

## Summary of changes
- add credentials for the jobs that run in containers

.github/workflows/benchmarking.yml

@@ -398,6 +398,9 @@ jobs:
     runs-on: ${{ matrix.runner }}
     container:
       image: ${{ matrix.image }}
+      credentials:
+        username: ${{ secrets.NEON_DOCKERHUB_USERNAME }}
+        password: ${{ secrets.NEON_DOCKERHUB_PASSWORD }}
       options: --init
 
     # Increase timeout to 8h, default timeout is 6h

.github/workflows/cloud-regress.yml

@@ -38,6 +38,9 @@ jobs:
     runs-on: us-east-2
     container:
       image: neondatabase/build-tools:pinned-bookworm
+      credentials:
+        username: ${{ secrets.NEON_DOCKERHUB_USERNAME }}
+        password: ${{ secrets.NEON_DOCKERHUB_PASSWORD }}
       options: --init
 
     steps: