CI/CD Hardening: Fixing StepSecurity Flagged Issues (#11724)

### Summary
I'm fixing one or more of the following CI/CD misconfigurations to
improve security. Please feel free to leave a comment if you think the
current permissions for the GITHUB_TOKEN should not be restricted so I
can take a note of it as accepted behaviour.

- Restrict permissions for GITHUB_TOKEN
- Add step-security/harden-runner
- Pin Actions to a full length commit SHA

### Security Fixes
will fix https://github.com/neondatabase/cloud/issues/26141

.github/workflows/check-permissions.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
     - name: Harden the runner (Audit all outbound calls)
-      uses: step-security/harden-runner@v2
+      uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
       with:
         egress-policy: audit
 

.github/workflows/cleanup-caches-by-a-branch.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Harden the runner (Audit all outbound calls)
-        uses: step-security/harden-runner@v2
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
         with:
           egress-policy: audit
 

.github/workflows/fast-forward.yml

@@ -14,7 +14,7 @@ jobs:
 
     steps:
       - name: Harden the runner (Audit all outbound calls)
-        uses: step-security/harden-runner@v2
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
         with:
           egress-policy: audit
 

.github/workflows/label-for-external-users.yml

@@ -28,7 +28,7 @@ jobs:
 
     steps:
     - name: Harden the runner (Audit all outbound calls)
-      uses: step-security/harden-runner@v2
+      uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
       with:
         egress-policy: audit
 
@@ -75,7 +75,7 @@ jobs:
 
     steps:
     - name: Harden the runner (Audit all outbound calls)
-      uses: step-security/harden-runner@v2
+      uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
       with:
         egress-policy: audit
 

.github/workflows/pin-build-tools-image.yml

@@ -41,7 +41,7 @@ jobs:
 
     steps:
       - name: Harden the runner (Audit all outbound calls)
-        uses: step-security/harden-runner@v2
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
         with:
           egress-policy: audit
 

.github/workflows/trigger-e2e-tests.yml

@@ -35,7 +35,7 @@ jobs:
 
     steps:
       - name: Harden the runner (Audit all outbound calls)
-        uses: step-security/harden-runner@v2
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
         with:
           egress-policy: audit
 
@@ -73,7 +73,7 @@ jobs:
         }}
     steps:
       - name: Harden the runner (Audit all outbound calls)
-        uses: step-security/harden-runner@v2
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
         with:
           egress-policy: audit