feat: prevent versioned 3P GitHub actions in PR builds (aws-observability#475)

Add validation step to require commit SHAs instead of version tags for
third-party GitHub actions in workflow files. Also fix the one we
missed: `aquasecurity/trivy-action` - depending on `master` is pretty
unusual and not trivial to catch, ultimately the Repo config `Require
actions to be pinned to a full-length commit SHA` will protect against
this if we missed any others.

### Testing done
* `Python Instrumentation PR Build / static-code-checks (pull_request)`
passes
* `Check CHANGELOG` fails, causing PR-build to fail, but `Check for
versioned GitHub action` passes:
https://github.com/aws-observability/aws-otel-python-instrumentation/actions/runs/17924516041/job/50967250100?pr=475
* Added various [`@v` in
code](aws-observability@f2f0523),
only finds uncommented ones:
https://github.com/aws-observability/aws-otel-python-instrumentation/actions/runs/17925754982/job/50971348934?pr=475
```
Found versioned GitHub actions. Use commit SHAs instead:
.github/actions/lambda_artifacts_build/action.yml:30:    - uses: actions/checkout@v4
.github/actions/lambda_artifacts_build/action.yml:42:    - uses: actions/checkout@v4 #v4
.github/workflows/daily-scan.yml:54:      - uses: actions/checkout@v4 #v4
.github/workflows/daily-scan.yml:106:      - uses: actions/checkout@v4
```

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

Author: thpierce

.github/actions/image_scan/action.yml

@@ -32,7 +32,7 @@ runs:
     run: docker logout public.ecr.aws
 
   - name: Run Trivy vulnerability scanner on image
-    uses: aquasecurity/trivy-action@master
+    uses: aquasecurity/trivy-action@b6643a29fecd7f34b3597bc6acb0a98b03d33ff8 # v0.33.1
     with:
       image-ref: ${{ inputs.image-ref }}
       severity: ${{ inputs.severity }}

.github/workflows/pr-build.yml

@@ -10,14 +10,15 @@ permissions:
   contents: read
 
 jobs:
-  changelog-check:
+  static-code-checks:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 #5.0.0
         with:
           fetch-depth: 0
 
       - name: Check CHANGELOG
+        if: always()
         run: |
           # Check if PR is from workflows bot or dependabot
           if [[ "${{ github.event.pull_request.user.login }}" == "aws-application-signals-bot" ]]; then
@@ -46,6 +47,24 @@ jobs:
           echo "It looks like you didn't add an entry to CHANGELOG.md. If this change affects the SDK behavior, please update CHANGELOG.md and link this PR in your entry. If this PR does not need a CHANGELOG entry, you can add the 'Skip Changelog' label to this PR."
           exit 1
 
+      - name: Check for versioned GitHub actions
+        if: always()
+        run: |
+          # Get changed GitHub workflow/action files
+          CHANGED_FILES=$(git diff --name-only origin/${{ github.base_ref }}..HEAD | grep -E "^\.github/(workflows|actions)/.*\.ya?ml$" || true)
+          
+          if [ -n "$CHANGED_FILES" ]; then
+            # Check for any versioned actions, excluding comments and this validation script
+            VIOLATIONS=$(grep -Hn "uses:.*@v" $CHANGED_FILES | grep -v "grep.*uses:.*@v" | grep -v "#.*@v" || true)
+            if [ -n "$VIOLATIONS" ]; then
+              echo "Found versioned GitHub actions. Use commit SHAs instead:"
+              echo "$VIOLATIONS"
+              exit 1
+            fi
+          fi
+          
+          echo "No versioned actions found in changed files"
+
   build:
     runs-on: ubuntu-latest
     strategy: