ci: Install oras when enforcing publishing from tags (#5965)

## Description

Align publish from tags workflow with publish github action

## Pipeline Reference

<!-- Insert your Pipeline Status Badge below -->

| Pipeline |
| -------- |


## Type of Change

<!-- Use the checkboxes [x] on the options that are relevant. -->

- Azure Verified Module updates:
- [ ] Bugfix containing backwards-compatible bug fixes, and I have NOT
bumped the MAJOR or MINOR version in `version.json`:
- [ ] Feature update backwards compatible feature updates, and I have
bumped the MINOR version in `version.json`.
- [ ] Breaking changes and I have bumped the MAJOR version in
`version.json`.
  - [ ] Update to documentation
- [x] Update to CI Environment or utilities (Non-module affecting
changes)

## Checklist

- [ ] I'm sure there are no other open Pull Requests for the same
update/change
- [ ] I have run `Set-AVMModule` locally to generate the supporting
module files.
- [ ] My corresponding pipelines / checks run clean and green without
any errors or warnings
- [ ] I have updated the module's CHANGELOG.md file with an entry for
the next version

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Author: eriqua

.github/workflows/platform.publish-tag.yml

@@ -42,6 +42,17 @@ jobs:
           sudo mv ./bicep /usr/local/bin/bicep
           bicep --version
 
+      # Adding a step to install Oras as it's only needed for publishing/validation
+      - name: Install Oras
+        shell: bash
+        run: |
+          VERSION="1.2.2"
+          curl -LO "https://github.com/oras-project/oras/releases/download/v${VERSION}/oras_${VERSION}_linux_amd64.tar.gz"
+          mkdir -p oras-install/
+          tar -zxf oras_${VERSION}_*.tar.gz -C oras-install/
+          sudo mv oras-install/oras /usr/local/bin/
+          rm -rf oras_${VERSION}_*.tar.gz oras-install/
+
       - name: "Publish tagged module to public bicep registry"
         id: publish_tag
         uses: azure/powershell@v2